The invention relates to the mechanical assembly of the door lock of vehicles, which comprises locking plate snap clip, key teeth identification device, locking plate automatic choosing device, automatic spring discharging and delivery device, locking plate snap clip moving device and its thrusting device, lock core jig and location exchange device, and embedded computer control system, with the method composed of key automatic location and identification, snap clip feeding and assembly, lock plate feeding and assembly, to finish the assembly of vehicle doors with accurate matching. Through lock core jig and location exchange device with the repetition of above procedures, it can get to the operation of next lock core. It is accurate, highly efficient, easy for operation, convenient for maintenance.