A quick-release structure for a grease gun includes: a cylinder including a peripheral wall and a fixing groove formed in an insertion section of the peripheral wall; the grease gun including an outer surface, an insertion hole, a slot formed in the outer surface and in communication with the insertion hole, the cylinder is inserted in the insertion hole and the fixing groove is aligned to the slot; a locking member inserted through the slot and into the fixing groove; a base fixed to the outer surface; an elastic member disposed between the base and the locking member; a press member including a press section and a drive section, the drive section is drivingly connected to the driven portion and to be pressed by a user; and a restricting member mounted on the base, and the press section of the press member leans against the restricting member.