The invention relates to a door lock outer protecting sheath proofing dust and dirt and resisting rain and snow. The outer protecting sheath comprises a base and a protecting sheath body. The base is provided with a hollow through channel matching with a door lock. The protecting sheath body is arranged on the base in a matched manner. The protecting sheath body is provided with a projection matching with the door lock in shapes. The projection is provided with an opening and closing baffle corresponding to a door lock key hole, and the opening and closing baffle matches with the key hole in shapes. The base matches with the protecting sheath body through rivets. During operation, the base is mounted at firstly, the protecting sheath body is combined with the base, and mounting is finished; when unlocking is required, the baffle is pushed aside, a key is inserted to unlock smoothly, influence on normal function of the door clock by outer factors is reduced, success rate for unlocking by staff is increased, and waste due to door lock damage is avoided.