A slide rail displacement positioning mechanism includes a slide rail assembly consisting of an inner slide rail and an outer slide rail, a stopper member affixed to the inner slide rail and providing a positioning gap between a frame body and an abutment component thereof, and a positioning member affixed to the outer slide rail and adapted for elastically biasing the abutment component upon a relative movement between the stopper member and the positioning member subject to the operation of the slide rail assembly, and thus, the positioning member can be positively stopped by the frame body to achieve relative positioning between the outer slide rail and inner slide rail of the slide rail assembly.