A federal appeals court here cleared the way yesterday for construction of a 95-room luxury hotel on the Georgetown waterfront, over the opposition of a group of environmentalists.

The $56 million project, including the four-story hotel and an adjacent five-story office building, will be built on a 1.2-acre tract between K Street NW and the Potomac River, along Rock Creek. The buildings will be part of the new Washington Harbour complex.

Construction on the site, which used to be occupied by a cement plant, had been limited to a height of 20 feet, but last year the National Park Service agreed that the new buildings could reach up to 60 feet in exchange for wide public walkways along Rock Creek and the Potomac waterfront.

The developers, Rosewood Hotels Inc. of Dallas, also agreed to spend more than $1 million for landscaping and restoration of a canal lock and to contribute $1 million toward development of a waterfront park west of Washington Harbour.

In May, U.S. District Judge Barrington D. Parker blocked the project, ruling that the Park Service had illegally rescinded the height restriction for development next to Rock Creek. But yesterday, a three-judge panel on the U.S. Court of Appeals said federal laws had been properly followed.

"It is not our place . . . to judge the wisdom of the proposed project," Judge Carl McGowan declared in a 21-page opinion, which said the restriction on Park Service actions that Parker and the opponents of the project had cited did not apply to the exchange arrangement.

"We're pleased with the decision because we feel it is important to have public access along the Potomac River and to Rock Creek," said Manus J. (Jack) Fish, the Park Service's regional director. "If it were not for the exchange, this would have been the only spot for 200 miles that would not have guaranteed public access to the river. And they also had the right to build up to Rock Creek . . . . We believe it's in the public interest to exchange the right for building heights above 20 feet to get public use of that land."

Cornish F. Hitchcock, a lawyer for the Public Citizen Litigation Group, who represented the four environmental groups that sued to block Rosewood's plans, expressed disappointment in the ruling.

He said his clients may ask the panel, which included Chief Judge Spottswood Robinson III and Judge Robert H. Bork, to reconsider its ruling, but added, "We're still sorting out the best thing to do next."

Plaintiffs in the case were the Committee of 100 on the Federal City, a group concerned with planning issues; the Human Environment Center; the Environmental Policy Institute, and the Committee for Washington's Riverfront Parks.

Yesterday Robert D. Zimmer, Rosewood's president, said construction will probably begin within 120 days. He said the hotel and office building, designed by architect Arthur Cotton Moore, will probably be completed by late 1987.