The seventh summer Spartakiade, the national sports festival of the U.S.S.R., was declared formally closed today with colorful ceremonies and the oft-repeated theme, "Now we are ready for the Olympic Games."

The flame of the Spartakiade, which had burned for 15 days atop Lenin Central Stadium, was extinguished at the conclusion of a 40-minute closing ceremony, and the emblem of the Spartakiade replaced by marching girls in leotards who formed the five interlocking rings symbolic of the Olympics.

The 101,000-seat stadium in the sprawling Luzhniki Sports Complex, which will be the hub of the Olympics next summer, was ablaze with the parading colors of the 15 Soviet republics, the cities of Moscow and Leningrad, and the 87 foreign nations that participated in the Spartakiade.

The closing festivities began with the sounding of the Kremlin chines, heralding a marching band and flag-bearers in formation, and ended with eight salvos of fireworks that exploded against the pale blue afternoon sky as the public address announcer intoned, "Farewell to Spartakiade, welcome Olympiad-80."

Meanwhile, officials of the Olympic Organizing Committee were already looking ahead 349 days - that number was mentioned often in a long day of the 22nd Olympiad on July 19, 1980.

"We have had ample opportunity to test the venues and our personnel for the forthcoming Olympic Games," said Anatoly Biriukov, a deputy mayor of Moscow.

While it is impossible to project from the experience of the past two weeks exactly how the first Olympics in a Communist country will go, many foreign officials and journalists were encouraged by the Soviet willingness to admit mistakes and seek solutions to problems that arose during the Spartakiade.

After a shaky start, considerable improvements were made in the organization of the games and the distribution of results and information, particularly in languages other than Russian.

The Olympic organizer acknowledged the major remaining flaws in their information system - especially the procedure of translating names into the Russian cyrillic alphabet before putting them into computers and then having to translate them back to their original alphabets, resulting in bizarre distortions and misspellings - and promised that these would be corrected.

Tricky political questions concerning the Olympics were skillfully side-stepped or deferred to the International Olympic Committee.

While declaring "The doors to Olympic Moscow will be tightly shut to the advocates of racism and apartheid," and courting the favor of black African nations with ringing denunciations of sporting contacts with South Africa and Rhodesia, Soviet officials studiously avoided any statements that might have encouraged boycotts by either Western or Third World nations.

Asked if countries which do not have friendly relations with the Soviet Union and were conspicuously not invited to the Spartakiade - including Israel and China - would be admitted next year, Vladimir Popov, vice president of the Olympic Organizating Committee, said:

"The accreditation of countries is the prerogative of the IOC, not the host nation. The athletes of any nation that is accepted by the IOC will be welcomed on an equal footing."

Westerners found it significant that on a tour of the Olympic Village - a complex of 18 16-story concrete buildings that will be turned into a fashionable and self-contained residential district after the games - Soviet officials pointed out the inclusion of a Jewish chapel.

The hosts are in the process of building 27,000 new hotel accommodations and training waiters, cab drivers and other support personnel in foreign languages and the niceties of comfortable travel, but they have a very long way to go to meet Western standards.

Visitors accustomed to Western luxury will undoubtedly find hotel rooms small and depressing, meals tiresome and ploddingly served, stores sparsely stocked and public toilets woefully inadequate. It will not be a deluxe Olympics, but if everything goes without chaos it will be considered a triumph.

The Spartakiade revealed little we did not already know about prospective medal winners next summer since most foreign countries did not send strong teams.

But the eight-lane Tartan track at Lenin Stadium proved softer and slower than expected. Times for sprints and intermediate distances were well off world records and personal bests. In most cases it is safe to assume that world records will be difficult to come by except in long distances.

The rowing basin at Krylatskoye has a "wind tunnel" problem similar to that at Montreal in 1976, with the inside lanes considerably faster than the windswept outside ones.

The shooting range in the Moscow suburb of Mysishchi - 70 minutes by car from the Olympic Village, the most outlying of the Moscow venues - has been highly acclaimed, as have been the archery fields, cycling circuits, fencing hall and equestrian venues.

The one construction site that remains far from completion is "Prospekt Mira" - literally, "Peace Avenue" - where a 40,000-seat domed stadium and covered facilities for swimming, diving gymnastics and basketball are being built. These buildings were conspicuously omitted from all tours during Spartakiade, but Popov expressed optimism. "All construction will be finished by the end of the year so that we can have test runs early in 1980," he said.