The invention discloses an automatic lock cylinder assembly machine which comprises a machine body and a rotating plate assembly with a lock cylinder arranged on the machine body, wherein an upper lock cylinder manipulator assembly, an upper spring assembly, a spring dection assembly, two upper lock plate assemblies, a key inserting manipulator assembly, a lock cylinder detection assembly, and a finish-product grabbing manipulator assembly are successively arranged along the clockwise circumference direction of the rotating plate assembly, wherein the finish-product grabbing manipulator assembly comprises a good product grabbing manipulator assembly and a defective product grabbing manipulator assembly; and the upper lock cylinder manipulator assembly, the key inserting manipulator assembly, the lock cylinder detection assembly, the good product grabbing manipulator assembly and the defective product grabbing manipulator assembly are all arranged on the rotating plate assembly, the rest assemblies are all arranged on the machine body, the machine body is provided with a bracing wire feeding mechanism for conveying the lock cylinder and a key to the corresponding position, and the assemblies are all connected with a master control circuit and are controlled by the master control circuit. The automatic lock cylinder assembly machine provided by the invention not only has the advantages of high production efficiency and low space capacity, but also ensures that the lock cylinder assembling quality is improved.