A national coalition of conservative and ethnic groups, encouraged by its apparent success in keeping the Soviet Union out of last year's Summer Olympic Games here, has begun campaigning for major changes in treatment of applicants for asylum from communist countries.

In a testy exchange of letters, meetings with State Department officials and the start of a lobbying effort in Congress, the Ban Coalition has decried government efforts to deport dissident Poles and Chinese. The group is demanding a looser interpretation of what constitutes "fear of persecution," the key element in deciding who is granted U.S. asylum.

"The State Department is 'selling out' defectors from communist countries and deporting them back to face human-rights persecution, concentration-slave labor camps, imprisonment and perhaps even death," David W. Balsiger, executive director of the Ban Coalition, said in letters to officials of the State Department and the Immigration and Naturalization Service.

Figures provided by coalition members indicate that 60 percent of applications for political asylum from communist countries other than Cuba have been denied since 1980.

The figures suggest that INS officials have been particularly hard on applicants from Marxist-oriented nations with fairly good relations with the United States. Figures for most of fiscal 1984 show that 92 percent of asylum applications from the People's Republic of China were rejected, while the denial rate for Soviet applicants was 49 percent.

The effort to lower the denial rate has produced conflict between conservatives outside the government who feel that any communist defector is an asset and those inside the government who feel that innocent people are being misused in an effort to loosen rules needed to discourage fraudulent asylum applications.

Responding to Balsiger's promise to publicize the case of a Chinese dissident whose asylum application was not supported by the State Department, Laura J. Dietrich, deputy assistant secretary for human rights and humanitarian affairs, wrote Oct. 31:

"Don't you think it is immoral to use an innocent individual as a public example to bolster your personal arguments over what is essentially a legislative debate? What do you think will happen to this gentleman's family back in the PRC China , after you have made him a public case?"

Dietrich's boss, Assistant Secretary of State Elliott Abrams, said in an interview that he has "a great deal of sympathy for some of the arguments" of groups supporting communist-bloc asylum applicants but that "they are coming to the wrong person in coming to me rather than to Congress."

Some conservative lobbyists insist that the State Department could grant many more applications without violating the law.

"The State Department has a history of not rocking the boat, and I think they are callous," said R. David Finzer, president of the Young Conservative Foundation Inc.

State Department officials have said that they view Ban Coalition as only one of several critics of the asylum process. The coalition's concern for defectors from communist countries is countered by concern for Salvadoran refugees escaping what they say are rightist death squads.

The State Department, Abrams said, is left with the chore of trying to apply the same standards to all cases.

Members of several organizations are visiting congressional offices to suggest revival of a law that, before 1980, gave special preference to asylum applicants from communist countries or Jewish applicants seeking asylum from Arab-ruled governments.

The Refugee Act of 1980 eliminated the preference, just as a glut of visitors from China and Eastern Europe swelled the numbers of asylum applicants.

Warren Leiden, executive director of the 1,700-member American Immigration Lawyers Association, said his group also is investigating changes needed in asylum procedures.

At present, he said, federal officials require "very substantial evidence" that applicants have a "fear of persecution if they return to their homeland," despite the defectors' unfamiliarity with U.S. law and the difficulty of obtaining documents from home.

The Ban Coalition is the reincarnation of the Ban the Soviets Coalition, the California-based group whose plans to encourage Soviet-bloc defections during the Summer Olympics were cited by Moscow as a major reason for its boycott of the Games.

The group, which says it represents 165 organizations, announced late last year a goal of orchestrating 269 defections from communist countries to commemorate the 269 persons who died when a Korean Air Lines passenger jet was shot down by a Soviet interceptor in 1983.

Finzer, whose group is part of the coalition, said the only congressional opposition that he anticipates is from the "radical pro-Soviet left," which sees communist societies in a more favorable light, and the "nut right," which wants no more foreigners allowed into the United States.

"If we have those two kinds of people opposing us, that's super," Finzer said.

Balsiger, an author and advertising executive who works out of his home in Costa Mesa, Calif., has also suggested that the INS provide each asylum applicant with an information sheet, preferably in his language, "which explains the Refugee Act of 1980, the asylum application and what significant information is being sought by the INS and the State Department."

Finzer, however, complained that one State Department official refused to provide him with such information on grounds it would help fraudulent applicants tailor applications to suit government rules on who is and is not a legitimate asylum candidate.

Some potential defectors, ordered deported after their asylum requests were denied, have managed to delay action on their cases through intervention of the Ban Coalition and have allowed Balsiger to use their names and statements in arguing for new rules.

Polish-born applicant Maria Sokulska of Costa Mesa was denied asylum after she told the INS that she would be "arrested . . . and possibly killed" for participating in anticommunist activities in Poland and the United States. She is now protected by a North Atlantic Treaty Organization agreement forbidding deportations to Poland.

A Chinese applicant, Mou Fengjie, was denied asylum despite evidence that he had been ruled a counterrevolutionary by a Peking court and had spoken against the Peking government at rallies in the United States.