A man grabbed a woman by the hair on a Brooklyn subway platform, then stole her glasses, authorities said.

The 36-year-old woman was waiting to board a northbound Q train at the Church Avenue station in Flatbush when a man grabbed her by the hair, yanking her to the ground, according to police sources.

The unidentified man then knocked off her glasses , snatched them and ran off, the sources said.

Police are still searching for the thief.

He is described as in his 20’s, and was last seen wearing a black baseball cap, black jacket, black pants and white sneakers.