Four Americans imprisoned on political and espionage charges in Cuba for more than a decade were returned here late today.

Wearing Cuban-issued suits and white shirts, they stepped off their State Department plane at Miami International Airport shortly before 8 p.m., thus completing an informal arrangement promised by Cuban President Fidel Castro. Their release followed President Carter's action on Sept. 10 freeing four Puerto Rican nationalists held on terrorist charges since the 1950's.

Their emotions ranged from the gratitude shown by Lawrence K. Lunt, 56, who served 14 years of a 30-year sentence on an espionage charge, to the tight-lipped defiance of Everett D. Jackson, who served almost 12 years of his 30-year sentence for violating Cuban air space.

Jackson, who parachuted into Cuba with news organization credentials and was "indirectly" working for the CIA, said he was not released but "deported," as he refused to be part of an arrangement that he said equated his efforts with the Puerto Ricans' attacks on former President Truman and the U.S. Congress in the 1950s.

The Carter administration also refused to link the two sets of prisoner releases and had avoided direct negotiations with Castro.

At an airport news conference, a third released prisoner, Juan Tur, 62, sat quietly with his Cuban wife and daughter, who were permitted to leave the country with him. Tur served 15 years of a 30-year espionage sentence. A relative has said he was a contract employe of the CIA.

The fourth released prison was Claudio Rodriguez Morales, a 49-year-old Puerto Rican who had served 13 years of a 20-year term for trying to smuggle refugees out of Cuba. After passing through customs and immigration, he left immediately for a flight to Puerto Rico.

Lunt, a rancher in Cuba, acknowledged he became a CIA contract employe in the early 1960; his ranch was in the same region where Soviet missiles were discovered in 1962. He said he did not regret his actions and believed that his time in prison was worth it, that he would "do anything for our country." He said, however, that he would "rather not answer" as to exactly what he did and that he had "served enough years."

"I was in the wrong place at the wrong time," said Jackson of his 1967 arrest after the crash of his small plane in the mountains of central Cuba. He said he carried credentials from a California newspaper, but that he intended to share his information -- whether there were still missiles in Cuba -- with the CIA.

Tonight he said: "I never got the chance."

The release of the four concluded several years of efforts by public officials and a lawyer retained by Lunt to win their freedom. Accompanying the men as they returned to the United States were two State Department officials, U.S. Reps. Benjamin Gilman (R-NY.) and Mickey Leland (D-Tex.), Wyoming Gov. Ed Herschier and Lunt's brother, Dr. John Lunt of Saratoga, Wyo.

Castro had said for at least two years that if the Americans freed the four Puerto Rican nationalists, he would reciprocate. President Carter granted clemency to the four Sept. 7 and they were released a week ago. This morning, Caban officials notified the United States that Tur, Lunt, Rodriquez Morales and Jackson would be released.

From the time they heard of Carter's decision on Cuban television, Lunt said, their release appeared certain. They were taken a short time later to a Cuban intelligence facility, then to an "immigration house" and this morning to the U.S. interest section in Cuba.

At 6 p.m. they were told their department was imminent. One hour and 45 minutes later they touched down on American soil.

Lunt, checking into the Marriott Hotel here, said there was "always a constant fear" that the arrangement would not go through. As for his feelings, the gaunt native New Englander said, "I have no feeling at all. The reaction has not set in."

The State Department said, "The United States is delighted," and Gilman described Castro's release of the four as a "gesture of humanism."

Rep. Leland, who had visited Cuba last year, described it as a "touching scene" today when Lunt's brother stood baffled after getting off the plane in Cuba, apparently waiting for some formality. "Go grab him," Leland told John Lunt, and the brother did just that. "Everybody," said Leland, "was in sort of a stupor."

White Rodriquez Morales was off to Puerto Rico and Tur was greeted in Miami by relatives from his hometown of Tampa, Fla., Lunt said he would be traveling to Washington and then to Wyoming, where he wants "to see if that worthless brother of mine will give me a job on his ranch."

Jackson, whose English bore a trace of Spanish accent, said he would visit his relatives in California and then perhaps return to Miami "to do a little writing."