The story of Eva Artemia Perez tells you a lot about how the human-rights situation in El Salvador has ''improved'' and yet how it remains a tragedy. A Christian Democrat and former mayor of this small town, Mrs. Artemia was caring for a three-day-old daughter Dec. 3 when leftist-led guerrillas struck. They damaged a military post, blew the roof off the mayor's office, and looted the health clinic.
Mrs. Artemia was unharmed, and it was apparently in part because of this that she was accused of cooperating with the guerrillas. On Dec. 4, government soldiers came to her house and arrested her. They seized a .22 caliber pistol, some bullets, and a piece of guerrilla literature dating back to 1977.
Mrs. Artemia tried to explain that a government military commander gave her the pistol for her protection when she was serving as mayor and that a sergeant in the government Army gave her the literature to show her ''what the Communists are saying.''
But there was more to the story than this. The current mayor of this town, located some 10 miles northeast of San Salvador, was a personal enemy of Mrs. Artemia. It was his denunciation of her as much as anything that appears to have led to her arrest.
The mayor, Pedro Guzman Flores, a military man and member of a political party that opposes Mrs. Artemia's Christian Democrats, accused her of helping to lead the guerrilla attack.
Leaders of the Christian Democratic Party, who have opposed the guerrillas and participated in the government, do not think the accusations against the former mayor are true. They point out that Mr. Guzman was reported once in the past to have threatened Mrs. Artemia's life.
The American ambassador in El Salvador, Deane Hinton, has doubts about Guzman's accusations as well. But the Christian Democrats and the ambassador cite Mrs. Artemia's case as an example of human-rights progress. It marks progress, they say, because not too many months ago, following the kind of accusations that have been made against her, Mrs. Artemia might have been summarily executed. As it is, she was separated from her child, kept in isolation for a few days, interrogated, then sent to a women'sprison in San Salvador. But she, and her child, survived the process. They are alive.
''She may or may not be guilty,'' Ambassador Hinton told this reporter recently. ''I have a lot of doubts about it. But previously, charged with what she's charged with, she'd have just been dead.''
The issue is of interest to the United States, because if the Reagan administration is to continue giving military aid to El Salvador, it must certify to the Congress by the end of this month that progress has been made in improving the human-rights situation in this Central American country. President Reagan has already stated publicly that, given what he knows, he will provide this certification.
The one thing that nearly everyone here seems to agree on is that the numbers of unarmed civilians being killed by death squads linked to the Salvadorean Army and security forces decreased in 1982. Almost everyone who follows the situation closely seems to agree as well that this is a result of American pressure on the Salvadorean government.
But the situation is far from ideal.
Even according to American Embassy figures, which are considered low by a number of human-rights groups, the number of deaths attributable to ''political violence'' - in other words, deaths caused by assassination and occurring outside the regular combat - will exceed 2,000 for 1982. In a recent interview, Ambassador Hinton said the numbers are ''way down'' but that they are still ''much, much too high.''
When it was pointed out to a Roman Catholic priest in San Salvador that the death squads seem to have stopped killing priests, he contended that this was because the security forces had succeeded in terrorizing most of the priests who criticized the government or sided with the guerrillas. Altogether, 11 priests were killed over the years, he said. A number of others were forced to leave the country.
Even after the killing of priests stopped, death squads still assassinated some religious teachers and pastoral workers.
''The persecution has achieved what they wanted,'' the priest said. ''. . .Among simple Christians, there is a lot of fear.''
''The number being killed is still absolutely intolerable,'' he said. ''The cruelty of the torture . . . continues. The numbers are lower. But is that an improvement? I would say no. Why? Because in my opinion the apparatus of repression remains basically intact. . . . The root of the thing has not been touched.''
Other critics point to some recent statements and incidents as evidence that the Salvadorean government and armed forces have not greatly improved their rights record:
* In an Oct. 3 homily, Bishop Arturo Rivera y Damas, and highest-ranking Roman Catholic in El Salvador, said, ''The impunity with which armed civilian groups act, at times in full daylight, gives the impression that something is missing in our application of the law and justice.'' Rivera had previously denounced the Salvadorean government for its failure to investigate a number of reports of mass killings.
* On Nov. 30, seven members of a cooperative farm, part of a social program of the Episcopal Church in El Salvador, were massacred in La Florida, 65 miles west of San Salvador. In sworn testimony, relatives of the victims, who were all males and heads of households, identified several of the men who had abducted the victims as members of the armed forces whom they knew personally.
* On Dec. 1, the families of four American churchwomen slain more than two years ago in El Salvador announced that they had decided not to hire a Salvadorean lawyer to represent them in the trial of five Salvadorean national guardsmen accused of the murders.
According to a spokesperson for the families, they found that Salvadorean lawyers who had been contacted feared for their lives, should they pursue leads suggesting that the five accused killers acted on orders from superior officers. The families charged that the lawyers did not believe the US Embassy in San Salvador was willing to support an investigation into the possible involvement of superiors. American officials deny this is the case.
When it comes to attacks on the Christian Democratic Party, Ambassador Hinton and others point out that, as is the case for the country as a whole, the number of assassinations has declined. But it is ironic that the Christian Democrats should be under pressure from the government security forces. This is a party that has committed itself to the anticommunist system. It got more votes than any other party in the last election. Yet it cannot protect its own members from assassination or arrest.
In an interview, Ambassador Hinton argued that there was an element of progress in the fact that fewer Christian Democrats had been killed in recent months and that a number of suspected killers of Christian Democrats had been arrested (although not yet convicted).
''Nothing like that had happened before,'' said Hinton, speaking of the arrests.
He added that these were small signs of progress in what remains a ''horrible situation.''
Eduardo Molina Olivares, a Christian Democrat and director of the Salvadorean Institute of Municipal Administration, say that nearly 300 Christian Democratic activists were assassinated between September 1980 and September 1982.
On the wall of his office, Molina keeps a photograph of a West German Christian Democratic leader, the late Chancellor Konrad Adenauer. He also has a map with green tacks on it showing where 37 Christian Democratic mayors were killed in recent years. Of the 37, he said, two were believed to have been killed by the guerrillas and the rest by local government military commanders and members of the government's security forces.
Molina said that most of the government's regular military officers were ''not bad people'' but that bad elements remain active.
''For 30 years in this country, anybody who has been against the government has been called a communist,'' Molina said.
For many of those years, the Christian Democrats have found themselves opposing military regimes.
When it came to Eva Artemia Perez, the now imprisoned ex-mayor of Oratorio de Concepcion, Molina said: ''The only thing we can be happy about is that they haven't killed her.''
The institute director said that Mrs. Artemia was a victim of ''personal vengeance'' on the part of the town's current mayor.
Marina Isabel de Ibarra, a Constituent Assembly deputy and friend of Mrs. Artemia, said that although there were fewer assassinations, there was still enough injustice in El Salvador to provide supporters for the guerrilla movement.
''Take this simple case,'' she said, referring to the arrest of Mrs. Artemia. ''When the military accuses a person of doing something, it is very difficult for that person to defend herself. . . . If the injustice continues, the guerrillas will win.''