Poland's Roman Catholic Church has taken a low profile since the imposition of military rule. But leaders of the church, to which more than 90 percent of Poles belong, now are making urgent efforts to:
* Help defuse the crisis.
* Salvage the ''dialogue'' that had put the Church's relations with the communist state on a unique footing since the mid-1970s.
Martial law has halted the activities of the trade union Solidarity. It has silenced all but official voices on the news media. But the Catholic Church still has a pulpit in every city, town, and village in Poland.
So far, it has made only cautious statements, pleading for the nation to remain calm and avoid bloodshed. Indeed, it is being criticized for being less outspoken now than it was during last year's battle for the union and for human rights. Some Catholics in Poland and the West are even charging Archbishop Josef Glemp with ''acquiescing'' in martial law.
But his predecessor, the late Stefan Cardinal Wyszynski, who had enormous influence with Poles, would not have disagreed with the message from Archbishop Glemp that was read in Polish churches Dec. 20: ''Avoid bloodshed,'' it said. ''Do not drive our country into greater disaster.''
The last three words are code words the Catholics have always used when their country was locked in crisis, with the everpresent threat of Soviet intervention looming especially large. Although the Kremlin is much more reluctant to intervene today than it was in 1956 or 1970, the words have even more meaning now.
For Poland's crisis is much greater this time. And it would be the Catholic Church - and the reform movement - that would suffer the greatest political setbacks. Hence church leaders in Poland - and the Polish Pope in Rome - are withholding judgment.
Only limited communication seems to have been maintained between church leaders in Warsaw and the Vatican until this past weekend. But then Pope John Paul II dispatched his own envoy, Archbishop Luigi Poggi, to Warsaw while the secretary of the Polish Bishops' Conference, Bishop Bronislaw Dabrowski, came to Rome.
One important subject on which the Pope has been briefed is the attitude of Solidarity leader Lech Walesa. Although Mr. Walesa is confined to a government lodging, Bishop Dabrowski was in constant contact with him until his own departure for Rome.
Meanwhile in Poland a group of Roman Catholic intellectuals and other churchmen have set up an ad hoc ''crisis staff'' in an attempt to maintain some links with the authorities. In particular, they are believed to be exploring the possibility of a new tripartite meeting of Archbishop Glemp, Mr. Walesa, and Gen. Wojciech Jaruzelski, the head of the ruling military council.
The three met in early December. But it is doubtful that any further meeting is possible during the present crisis. Mr. Walesa is reliably said to have refused to meet with General Jaruzelski until he is allowed to confer with Archbishop Glemp. And the primate won't talk with the authorities unless and until Walesa is able to participate freely.
At present there is no prospect for a renewal of church-state dialogue without some substantial gesture or reassurance by the authorities. Although the curfew is being lifted for the Christmas Eve midnight mass, any major gesture looks a long way off, as does any early or genuine resumption of the reform program.
Yet peace is unlikely to come to Poland without some accommodation between its present military ruler and the two men - union leader and primate - who retain the allegiance of most Poles.