President Carter made a spirited defense of his economic record here today and said that, while there is "room for improvement," Americans have a lot to be thankful for this Christmas.

In a sidewalk news conference outside his cousin Hugh Carter's antique and gift shop, Carter took particular issue with the suggestion by some of Ronald Reagan's advisers that the president-elect declare an immediate state of economic emergency on taking office.

"For anyone to declare an emergency would arouse a psychological reaction that would very likely damage the economy," creating an unwarranted "sense of panic," Carter said.

"I don't think that ought to be done and don't think it will be done," he said of the proposal that Reagan's most senior advisers have downplayed in recent days.

While Reagan turned the economy into a major campaign issue, Carter seemed to find only upbeat news to bolster his economic optimism in the last weeks of his presidency.

"In general," he said, "we have a strong economy and have set all-time records in many elements of economic prosperity and benefits to our people and I'm very proud of what we've done . . . so we have a lot to be thankful for in this country."

"The value of the dollar is high," he said. "We have had the highest trade balance this quarter of any in history except one in 1975. Employment is the highest it has ever been in the history of our country. The American people's income has been higher than has the inflation rate."

Government indices support most of these contentions, although there are some conflicting trends. The dollar as been particularly strong this year measured against many other currencies. Counting services as well as goods, the United States had a $4.9 billion trade surplus in the third quarter. During Carter's term, the labor force has grown substantially and the current unemployment rate of 7.5 percent is slightly lower than the 8 percent he inherited when he took office.

Also, while inflation is running at an annual rate of 12.6 percent this year and has been high throughout the Carter term, Americans' per capita after-tax income has risen 7.3 percent during Carter's presidency even after adjusting for increases in the cost of living. During the same period, however, hourly earnings dropped 5 percent in real terms.

Carter blamed "excessively high" inflation on foreign oil price increases. "Of course," he said "interest rates are too high also. But you can't have everything perfect."

Carter also said he was buoyed by the recently announced third quarter growth rate of 2.5 percent, signaling an apparent end to the recession. The new figure, following a 9.9 percent drop the second quarter, "was higher than we had anticipated," he said.

Contrasted with Carter's optimism over the economy was his pessimistic view of the outlook for release of the U.S. hostages in Iran during his final days in office. Prospects for any such early release, he said, are "unfortunately quite dim."

During the 15-minute news conference that interrupted a traditional Carter walk along Plains' single main street, the president spoke also of the Soviet invasion of Afghanistan last Dec. 27. It was, he said, a "serious mistake" that had cost the Soviets economically with the American grain embargo and politically with the "world-wide public condemnation of their aggression."

The Carter family spent an hour Tuesday afternoon visiting the president's mother, Miss Lillian, who is recuperating from a hip injury.

And today, he paid a Christmas Eve visit to downtown Plains, a jumble of tourist shops and a handful of other businesses. As he walked the few blocks from his home, hand in hand with his wife, Rosalynn, Carter apologized to a motorist who had been stopped to make way for his arrival.

About 100 people, many of them tourists, ogled the Carters as they went from shop to shop, greeting owners and patrons. At the office of the Plains Monitor, the local newspaper which has just changed hands, the Carters received a bicycle built for two as a Christmas gift.

Carter told the new publisher he would soon send him a new reporter, daughter Amy, who "can write well and she can even spell." Jana Theus, daughter of presidential brother Billy, is already on the staff.

After their walk, the Carters, dressed comfortably for the mild weather and informal setting, rode their new bicycle home. Following the cycling couple were jogging reporters and film crews and three official cars.