The United States last year imported $612 million worth of Iranian goods, mainly crude oil but also caviar, furs, Persian carpets, spices and gems.

Iran bought a relatively small amount of U.S. goods in the same period, spending $34 million on less exotic items such as construction material, agricultural machinery and live animals.

Most of the Iranian trade with the United States involved $505.8 million in crude oil, a Commerce Department official said.

The figures do not include $30 million in secret U.S. sales of TOW antitank missiles and Hawk antiaircraft missile parts. Even if those sales were included, the Commerce Department figures show that U.S.-Iranian trade remains at a trickle seven years after the takeover of the U.S. Embassy in Tehran. The administration is discussing further trade restrictions on Iran.

The largest item on the $107 million luxury shopping list that makes up the remaining imports was close to $55 million of carpets. The U.S. confection trade bought $15 million in pistachio and other "edible nuts," and $6.2 million in Iranian antiques was imported last year.

Iranian caviar worth more than $2 million was imported, along with about $2 million in furs and leather.

Glassware, shellfish, spices and gems accounted for $5.2 million in trade.

Iran also exported $2.4 million in office machines to the United States. These were probably "re-exports," the official said.

Last year Iran bought $1.7 million in U.S. cars; $15 million in construction materials, including boilers, elevators and winches; and $3 million in electrical machinery.

The offical said the electrical machinery did not include computers. The Reagan administration last year approved export licenses for $900,000 in computers for Iran, although the Defense Department objected strongly.

"The allowance went through, but the sale of computers to Iran did not," the official said, because Iran found another source. This is contradicted by news reports from Iran that the Energy Ministry did purchase a $900,000 computer from the United States in April this year. The computer was to be used to control the electrical supply in Tehran, the reports said.

A second computer destined for the Islamic Republic News Agency was never bought, the reports said, because the agency purchased another computer.

The United States spent $418.5 million on Iranian imports in the first five months of this year, a State Department spokesman said. This did not indicate an increase in trade between the two countries this year, he said, but was probably due to seasonal fluctuations in the spot price and demand for oil.

U.S.-Iranian trade slackened after the 1979 takeover of the U.S. Embassy in Tehran, when 52 American hostages were held for 444 days, officials said.

In 1982, oil imports from Iran dropped sharply, when the United States bought $540 million in petroleum and petroleum products, a State Department official said.

Figures show, however, that oil sales almost doubled in 1983, when the United States imported $1.129 billion in Iranian goods, including $1.63 billion in petroleum products.

Trade dropped again in 1984, when U.S. imports almost halved to $679 million. This rose slightly to $715 million in 1985, and dropped back last year to $612 million.

Since the 1983 boom year, U.S. exports to Iran have been steadily cut. Exports to that country were more than halved from $137 million in 1984 to $64 million in 1985, and dropped again last year to $34 million.