The present invention discloses a door lock cipher device which is composed of a casing, a cipher body and a pulling plug. The end of pulling plug is installed with a connecting component connected with the locking bolt of door lock. The cipher body is a stepped shaft with a wide middle part and two thin end parts. The stepped shaft is longitudinally installed in the casing. The thin parts at two ends of stepped shaft transverse the front-back wall of casing and extend to the outside of casing. Two ends of stepped shaft are installed with cipher knobs. The middle wide part of stepped shaft is radially manufactured with a firing pin installing hole. An automatic reset firing pin is installed in the firing-pin installing hole. The length of firing pin is equal with the diameter of middle wide part of stepped shaft. Two ends of firing pin and the periphery surface of middle wide part of stepped shaft have a smooth transition. After the cipher is aligned, the firing pin and the pulling plug are in a line. The key pulling plug of rotating door lock is inserted into a firing pin installing hole through parallel moving, and the firing pin is pushed out. According to the door lock cipher device of the invention, the door can not be opened even the theft unlocks the door lock technically or destructively.