The utility model discloses a chlorine cylinder valve replacing device, which is characterized in that: the utility model comprises a big sealed chamber and a small sealed chamber, a press ring arranged on the front end of the small sealed chamber, two screw rods which are separately arranged on the small sealed chamber through a fixing hole and a stuffing box; a connection sleeve connected with the stuffing box is arranged the screw rod at the upper part; an operation rod is arranged at the top end of the screw rod; an inlet and an outlet gas ball valve are separately arranged on the upper and the lower cavity wall of the big sealed chamber. The utility model has the advantages of having the ability of being disassembled and arranged for the chlorine cylinder valve under closed status, avoiding chlorine leaking, polluting environment and impairments and improving the efficiency of replacing the chlorine cylinder valve.