Marriott Corp. profits soared 39 percent last year to a record $54 million on sales of $1.25 billion, the Bethesda hotel and restaurant company reported yesterday.

Separately, a company spokesman said that earlier plans for a Washington area amusement park have been all but abandoned. "It is still a possibility but the chances are slim," said senior vice president Thomas Burke of Marriott's original plans for a theme park that would require an investment of more than $50 million here.

Announcing earnings results on a calendar year basis for the first time, to reflect a change in fiscal years, Marriott said earnings per share in 1978 were $1.43 compared with $1.04 the previous year, when total net income was $39 million.

The revenues last year were up 15 percent from $1.09 billion in calendar 1977 and President J.W. Marriott Jr. said all five major business operations posted sales and profit gains.

"We were tested in several critical areas the past year," Marriott stated. "The federal minimum wage jumped 15 percent overnight at the beginning of 1978 and pushed up our biggest cost of doing business... food costs also rose... but we served a record number of people in our hotels, restaurants and other operations."

Providing details on various company operations, Marriott said:

Hotel sales rose 22 percent and profits were up 23 percent; average occupancy of rooms exceeded 80 percent -- the highest in the industry -- as four new hotels were opened, increasing total rooms by 17 percent to 18,000.

Contract food services profits rose 11 percent on a 13 percent sales increase, despite lower earnings in U.S. airline catering -- the single biggest division.

Restaurant profits rose 6 percent on a 10 percent sales gain, with earnings down for the two smallest divisions -- Hot Shoppes and dinner houses. The firm listed $1.1 million in reserves and losses related to a "deliberate program to dispose of low-yielding assets..."

Amusement park earnings "improved markedly" with third-year attendance at the firm's two parks reaching a record 5.2 million last year; profits rose 18 percent on a 5 percent sales increase.

Sun Line cruises, Marriott's smallest major business line, posted "modest" gains.

President Marriott also noted yesterday that interest costs declined after the sale of five hotels last summer, which continue to be managed by the firm, and the sale of excess land near its California amusement park.

As reported earlier, Marriott has written off in calendar 1978 the $1.4 million of costs related to an abortive attempt to build a major theme park -- either in the Manassas area or in Howard County. Two times, a Marriott park plan was rejected in Howard County and disputes over access roads helped to kill the Virginia park.

Burke said yesterday that various studies on an area park have been completed and that it is unlikely Marriott could profit from such a huge investment at this time -- particularly because of the two theme parks near Richmond as well as Hershey Park in Pennsylvania, all in the larger regional marketplace.

At this time, Marriott is not engaged in active consideration of other sites for amusement parks elsewhere in the nation but Burke said the company has no plans to sell the existing parks it started three years ago.

President Marriott forecast yesterday that 1979 will be another record year with advance hotel bookings strong and restaurants expecting a good year after a slow first quarter. Return on equity reached 14.8 percent last year compared with 12 percent in 1977 and a low of 10.3 percent in 1975.

Marriott previously reported earnings on the basis of a fiscal year that ended in July.