The federal government, no longer burdened by the Iranian crisis and confident that the Cuban refugee problem is under control, has resumed long-stalled efforts to deport thousands of Haitian boat people and other foreigners.

The crackdown on Haitians in this country illegally, which began last week when a Haitian woman was ordered deported by an immigration judge in Miami, could eventually affect as many as 4,000 people who have fled the Caribbean island in the last six months. It was the first Haitian deportation from this country in almost two years.

The move to exclude Haitians from the United States comes at a time when the Immigration and Naturalization Service is preparing to crack down on thousands of other foreigners who are working illegally here and elsewhere in the country.

Officials say they will resume large-scale searches of businesses here looking for illegal aliens. Such searches had been curtailed during the taking of the 1980 census because census takers feared INS arrests might interefere with their work.

The release of American hostages by Iran has erased one problem that has plagued the INS -- the search for Iranians here illegally. That, coupled with the end of the Cuban refugee exodus, will enable investigators to concentrate on the illegal presence of other foreign workers.

An INS spokesman said yesterday that apprehensions of other illegal aliens, which recently had been running about 10 percent below normal, should increase dramatically, perhaps by as much as 20 percent.

"We anticipate increased apprehensions," said spokesman Vern Jervis. "Apprehensions, which had fallen to 920,000, will almost certainly be back over a million this year, and that's always the best measurement of the effectiveness of our enforcement efforts."

The decision to begin to deport Haitians illegally here was made in mid-January by the Justice Department after an appeals court overturned a two-year-old court order baring such an action.

Currently, it is said, there are 4,785 Haitians subject to possible deportation. All of them entered the country after Oct. 10, 1980.

Those who arrived on that date or before are protected by a Justice Department order allowing them to stay while legislation that would permit them eventually to become permanent residents is debated in Congress.

Not all the 4,785 Haitians are likely to be deported, however, Jervis said. Most of them have applied for political asylum, citing political repression in their homeland. Those applications may take up to a year to review.

Rick Schwartz, a Washington-based lawyer who has represented the Haitians, said the resumption of deportations is causing serious problems not only for the Haitians, but for the Florida communities they are living in.

Volunteer agencies that already have helped relocate almost 900 of them are now balking at relocating any more because of the threat of eventual deportation, he said.