Sergei Bubka of the Soviet Union broke his world pole vault record yesterday, clearing 19 feet 8 1/4 inches at the Paris International track and field meet.

On his third attempt, 22-year-old Bubka shattered the record of 19-5 3/4 that he set Aug. 31 in Rome. He slightly touched the crossbar with his chest on the record-setting, 6-meter jump, but the bar held firm. Raising his arms high, he was immediately mobbed by well-wishers.

Bubka's effort overshadowed a fine performance by Mary Slaney of the United States in the women's 1,500 meters.

Slaney, in her last meet before her long-awaited matchup with Zola Budd in London Saturday, won in 3 minutes 59.84 seconds. It was the best 1,500-meter time of the season, although far short of the world record of 3:52.47 set by Tatiana Kazankina of the Soviet Union on Aug. 13, 1981 . . .

In the British Amateur Athletics Association meet in London, Willie Banks of the United States. won the triple jump at 56 feet 6 inches, well short of the world record of 58-11 1/2 he set last month in Indianapolis. Ernest Obeng, a London-based Ghanaian, edged U.S. sprinter Darwin Cook in the 100 meters, 10.44 seconds to 10.45.