The usually tranquil southern Caribbean island of Grenada - home of a mere 110,000 people - has been the center of a storm of controversy. President Reagan added to that controversy this week, complaining anew about the island's ''Soviet-Cuban militarization.''
Singling out Grenada's Cuban-built airfield, whose 10,000-foot runway is easily the best in the eastern Caribbean, the President noted, ''Grenada doesn't even have an air force. Who is (the airfield) intended for?''
The Reagan administration says the airfield will be used by Cuba to supply its troops in Angola, and that it gives Cuban jets enhanced refueling facilities , improving the Cuban Air Force's flexibility.
Many of Grenada's neighboring leaders are also uneasy over the Grenada-Cuba link - a relationship Prime Minister Maurice Bishop admits ''with pride.'' But this uneasiness has not reached the point of anxiety, nor does it suggest that the countries of the region are ready to join Washington in any collective action against Grenada.
Reagan administration officials, nevertheless, are making much more of Grenada's Cuba connection than ever before. They recently began calling the island the ''virtual surrogate'' of Cuba. They also charge that the Cubans have built a batallion-size military camp on the island.
The US would like nothing better than to isolate Grenada in the area. But Washington knows it must tread carefully. Regional fraternity makes it difficult for some neighbors to speak out against Grenada's Cuba links.
Yet those links exist. Grenada's prime minister has visited Cuba several times in the past two years. He frequently has harsh words for the US, this week warning of a US plot to oust his government.
He says Grenada is not a part of the US sphere of influence: ''We do not live in anybody's backyard, and we are not accepting the right of America or anyone to instruct us on our foreign affairs.''