"Keep it Kicking!" an exhibition of New York's Radio City Music Hall, opened last night at Washington's Pension Building.

It was brought here by the Heritage Conservation and Recreation Service, a government agency recently created to administer President Carter's National Heritage Program. The new agency obviously considers the Art Deco splendor of the great music hall not only recreation but also part of our heritage worth saving.

The theater's interior was declared a national landmark two months ago, but its future is still in doubt. The owners, the Rockefeller Center Corp., threatened to close it last spring, claiming multimillion dollar deficits.

A last-minute reprieve came when the New York Urban Development Corp., promised to come up with a profitable use by this fall. The New York City landmarks commission, meanwhile, denied a dernolition permit. So the famous Rockettes are still at it this summer.

Keeping them kicking will largely depend on popular understanding that Radio City Music Hall, with its many paintings, murals and sculptures and its exuberant, unique design of every detail down to the fire hose containers and ash trays, is one of America's great cultural accomplishments.

The color photographs by Bo Barker convey this accomplishment, but do not add up to an impressive exhibition. A few pieces of Art Deco furniture, lent by Rockefeller Center, are nifty, but do not help much.

Yet, it is a public service that the Pension Building (at 4th and F streets NW, Judiciary Square Metrorail stop) is used for such exhibits, until plans to turn it into an architecture and urban design museum are worked out.

The Radio City Music Hall show runs until Aug. 11.