Accusing a fellow rider of fondling her, a 27-year-old Queens woman angrily dragged a 31-year-old man off a crowded Lexington Avenue subway train Friday morning below Grand Central Terminal and beat him, according to the transit police.

So overwhelmed was the man that he apologized while the woman was beating him, and he asked a subway conductor to call the police, according to a spokesman for the transit police, Albert W. O'Leary Jr. The man and the woman each filed a complaint against the other, Mr. O'Leary said. The man was arrested on a charge of third-degree sexual abuse, he said, and the woman was issued a criminal summons for harassment.

Mr. O'Leary said he had not observed either participant in the subway drama and could not account for the woman's ability to overpower the man. He said she described herself in a telephone conversation with him simply as being 5 foot 6 inches tall. 
The man was identified as Robert Davidson of 301 East 64th Street. As a possible sex-crime v''She was extremely angry,'' Mr. O'Leary said. ''She indicated she had heard of this kind of thing happening but it had never happened to her. She was incensed.''

The incident occurred about 8:40 A.M. aboard a southbound No. 4 train.

The man and woman, he said, were in a crowded subway car standing near the doors when the man began fondling her. The woman tried to move away, but other passengers, unaware of what was happening, complained that she was crowding them.

After the woman protested out loud about what the man was doing, other passengers moved out of her way, Mr. O'Leary said. With enough room to turn around, ''she began slapping him and punching him around the head and shoulders.''

When the doors finally opened, Mr. O'Leary said, the woman ''grabbed him by the collar and yanked him off the train onto the platform. She knocked him down and began slamming his head against the platform.''

It was then that Mr. Davidson was said to have apologized and asked for the police, he said.