Commerce Secretary Malcolm Baldrige yesterday said that if the Soviet Union liberalizes its stand on immigration and human rights, the Reagan administration might lift export restrictions on sensitive petroleum-drilling and exploration equipment.

Baldrige, testifying before the Senate Banking Committee, called the release last week of Soviet dissident Anatoly Shcharansky "a good start." But he indicated that more would be required from Moscow, especially in increasing the number of Soviet Jews allowed to immigrate to Israel, before the U.S. would lift its 6 1/2-year-old curbs on sales of drilling gear.

American manufacturers claim the restrictions have cost them at least $1.8 billion in Soviet business to competitors in Western Europe and Japan, but have not produced any major changes in Moscow's policies on human rights or immigration.

Nonetheless, the Reagan administration last month renewed the restrictions on the sale of oil and gas exploration and drilling equipment to the Soviets in a slightly loosened way.

Instead of an almost automatic denial of permission to export the gear, administration policy now allows for a case-by-case review based on U.S. foreign policy considerations.

Under sharp questioning by Sen. John Heinz (R-Pa.), Baldrige said loosening the regulations will allow the administration to respond by approving individual sales "if relations continue to improve, if we see additional special steps toward immigration and human rights" on the part of the Soviets.

Baldrige called the steps taken by the Soviets recently in improving relations with Washington in the fields of trade, arms control and cultural exchanges "modest" and "a good beginning."

Industry officials said the slight relaxation of restrictions by the administration were not enough to persuade the Soviets to start buying American oil and gas drilling equipment again. They said the Soviet market is "the largest in the world and is likely to remain so for some time to come," despite the oil glut that has slowed drilling in most of the world.

The restrictions were put in place in July 1978 to show the Carter administration's displeasure with Moscow's imprisonment of dissidents Shcharansky and Alexander Ginzburg. Both have since been freed.

At that time, as much as 45 percent of total western exports of oil and gas drilling and exploration equipment into the Soviet Union came from the United States.

In 1983, the Petroleum Equipment Suppliers Association estimated U.S. exports were $6.8 million, or 0.04 percent, of the $1.7 billion in Soviet purchases from noncommunist sources. The Soviets bought "a meager $557,000" worth of oil and gas exploration equipment during the first 10 months of last year, the industry said.

Administration and industry sources said a secret report by the Central Intelligence Agency shows that American allies in Western Europe -- who refused to go along with the U.S. embargo -- gained most of the Soviet business.

West Germany and Italy have emerged as the top two suppliers of oil and gas drilling and exploration equipment to Moscow, followed by Romania, the only Communist Bloc nation among the first five, industry sources said. France is the fourth-largest supplier, while Japan, which in 1978 had no sales of oil and gas drilling equipment to Moscow, is fifth.

Baldrige said trade restrictions seem to be "first on everyone's list" when it comes to some form of nonmilitary sanctions to buttress a U.S. foreign-policy position.

"As secretary of commerce," he said, "I wish there were other ways to show our displeasure other than turning off the trade spigot."