A former official of the Immigration and Naturalization Service, who admitted he took $22,000 in payoffs from wealthy Iranians and other foreigners for his help with their immigration problems, was sentenced in federal court yesterday to serve a minimum of six months in jail and pay a $20,000 fine.

Federal prosecutors had alleged that the defendant, Maron J. (Babe) Sheehi, 55, of Alexandria, secretly set up an immigration consulting business in December 1978 and charged his affluent clients as much as $10,000 to oversee their cases as they were processed through INS, where he had worked for 28 years.

Clients were steered to Sheehi's business by members of the Iranian community who in turn were paid a cash "finder's fee" for their work, prosecutors said. The business was named after Sheehi's girlfriend at the time, Maria Victoria Carballo, a Costa Rican, and a Palestinian friend. Neither of the latter two was charged.

According to government prosecutors, the partnership was dissolved in late 1979 after the Iranian takeover of the American Embassy in Tehran made it "virtually impossible" to process Iranian immigration cases.

Sheehi, who had been an immigration inspector at INS headquarters in Washington, pleaded guilty in July to one count of conspiracy to accept bribes and illegal gifts and one count of tax evasion. Yesterday, U.S. District Judge Thomas A. Flannery sentenced Sheehi to serve consecutive prison terms of three to 18 months on the two charges. Flannery also ordered Sheehi to pay a $20,000 fine within one month.

According to court records, Sheehi would advise Carballo on how to handle residency applications, assisted her in filing proper immigration documents and told her which employes to seek out and which to avoid at the INS Washington district office.

In February 1979, Shams Javid, an Iranian national, was paid $500 after he referred a former colonel in the Iranian police force who paid a $3,000 fee to the firm for help with an application for permanent residency, court papers said. When a problem arose with that application at INS, Javid consulted with Sheehi, changes were made in the form and the colonel was awarded permanent residency here.

In another case described in court papers, Javid "steered" an Iranian couple living in the New York area to the firm to process applications for permanent residency. Sheehi was introduced to the couple as "Joseph, the immigration lawyer" and a $10,000 fee was paid, court records said. The couple has not yet received permanent residency status, the government said.

Sheehi also helped get a U.S. passport for the daughter of an Iranian diplomat by destroying a State Department document that would have revealed that she was an Iranian citizen and thus not eligible for that passport, according to court papers filed by assistant U.S. attorneys Charles J. Harkins and Robert R. Chapman. Justice Department lawyer Bernard J. Panetta II also joined in the case.