American parents whose children have been jailed in Bolivia for as long as three years without trial on drug charges, held a prayer meeting at the main entrance to the State Department yesterday to dramatize what they see as a lack of response to the problem by the Carter administration.

About 25 members of Concerned Parents, an organization formed to secure the release of the American prisoners, denounced the Bolivian government for holding their children in prolonged custody without due process of law and under what they described as inhumane conditions.

The demonstrators asserted that their sons and daughters had been arrested under a tough drug law enacted with the advice of the United States government and by agents who had been trained and equipped by Americans.

"This government put them in prison and this government can get them out," said William Farmer of Dallas, one of the three cofounders of Concerned Parents.

Farmer's son, Richard, has been charged with trafficking in cocain. "On the basis of circumstantial evidence he's been in prison for 25 months without sentencing," Farmer said.

Farmer, who said his son was a frequent visitor to Bolivia on business, said his group represents 32 Americans in Bolivan prisons. The State Department says there currently are 33 U.S. citizens jailed in that country.

Mothers, several of whom cried during the brief protest, said their children were not given proper medical attention and that some of them had been tortured.

Louis G. Field, a State Department lawyer who visited Bolivia in late January and early February as a member of an official three-man investigative team, said that he had spoken with all the American prisoners and had found no evidence of serious injuries caused by torture. He said the prisoners had been asked to come forth with any accusations of torture, but that none did.

Fields described Bolivian officials as being "reasonaly noncommital to us" about the prisoner problem. He said they had promised to try to speed up the judicial process and that since his visit, two judges had been added in the capital of La Paz.