The nation's trade deficit doubled to $5.6 billion in the final quarter of 1980 as the volume of exports dropped while imports rose, the Commerce Department reported yesterday.However, the deficit was still less than those in the first and second quarters of the year.

Oil imports jumped by a sharp 11 percent during the quarter, as buying resumed for the Strategic Petroleum Reserve. Other imports increased by 3 percent, or $1.2 billion, to $43 billion for the three months.

Meanwhile, the Commerce report shows exports rose by only 2 percent in value. This was less than the increase in export prices, so that the volume of American goods sold overseas actually dropped during the quarter by 1 percent.

Yesterday's figures are seasonally adjusted and on a balance-of-payments basis, which means the export and import figures are comparably measured. They show that for 1980 as a whole the nation's trade deficit shrank to $26.7 billion from $29.4 billion the previous year.

Once "invisible" items, such as shipping, travel and dividends from overseas, are included, the nation was probably in surplus on its payments last year. This means that the U.S. earned more from its overseas operations and sales than was spent on foreign goods and services.

Total imports, including oil, rose by 5 percent in the last quarter of 1980 to reach $62.1 billion. Exports rose by $400 million to $56.6 billion. Three-fifths of the import climb was due to higher prices, leaving a rise of 2 percent in the amount of goods bought from overseas.

Last year's trade gap seesawed from $10.8 billion in the first quarter of the year, when the economy was growing very rapidly and drawing in imports, to the low $2.8 billion deficit in the third quarter. The revival in the economy in the final months of last year probably accounted for some of the worsening in trade performance.

Many of the U.S.'s trading partners have begun to move into recession, cutting down their demand for American exports. At the same time the dollar has risen sharply in value against other foreign currencies, notably the German mark. While this reflects in part the improved trade performance in the U.S. this year, it also makes it harder for U.S. firms to sell overseas as their goods cost more in foreign currency.

The U.S. trade deficits with OPEC, Japan and Canada widened during the fourth quarter, while the surplus with non-OPEC dveloping countries also grew. During 1980 as a whole, the U.S. shifted into surplus with the non-oil developing countries, and increased its surplus with Western Europe from $12.3 billion to $20.3 billion.

Exports rose by 22 percent from 1979 with an 8 percent increase in volume terms and the rest accounted for by higher prices. Imports went up by 18 percent during the year, with higher prices more than accounting for the increase. The volume of imports dropped by 3 percent from 1979.