The top-seeded team of Clark Graebner and Doug Russell gained today's semifinal of the $13,680 Passport Grand Prix of platform tennis by defeating Bill Ayres and Graig Mielke, 6-0, 6-3, yesterday at Columbia Country Club.

Semifinal play gets under way at 10:30 a.m. today with the final scheduled for 1 p.m.

Platform tennis, doubles at major tournaments, is played on a smaller court, surrounded by a 12-foot wire screen, which keeps the ball in play. Only one serve, rather than two, is permitted.

Graebner and Russell lead the circuit with 376.8 points. In second place at 33' are Harb Fitz Gibbon and Hank Irvine. They were upset yesterday by unseeded Greg Brents and Rich Maier, 4-6, 7-6, 6-4.

Russell, 35, the only full-time platform tennis professional on our, said, "We played them (Ayers-Mielke) five times this year and have lost only once, so we knew what to expect. We sometimes even practice together."

Russell took up platform tennis 11 years ago after winning the club championship at Forest Hills.

"A friend asked me to play platform tennis one day and I immediately lided it. I had always liked doubles better than singles and I said if I'm ever going to be a national or world champion, this is going to be my sport."

By 1976, he had won the world championship.

Five years ago, Russell gave up a position on Wall Street to pursue platform tennis on a full-time basis. He is director of the Apple Platform Tennis Club in New York City and has written two books on the sport.

Graebner, 36, a former top-ranked Davis Cup player, left tennis for more than two years. He took up platform play to get more exercise. Off court he works in New York's financial district.

In other quarterfinal matches yesterday, brothers Chip and Steve Baird rallied to defeat Mike Burton and Duke Felt, 4-6, 6-2, 6-1.

Fourth-seeded John Adams and John Mangan also advanced to the semifinals by defeating Mike Ducey and Jim Symington, 6-3, 6-3.

Adams and Mangan will play Graebner and Russell.