The invention discloses an automatic pull-in mounting device and an automatic pull-in mounting method for a motor and a worm. The automatic pull-in mounting device comprises a cylinder, a bottom plate, a motor seat, a linear bearing plate, a supporting shaft and a shaft bracket, wherein the bottom plate is arranged horizontally; the cylinder, the motor seat and the shaft bracket are all fixedly mounted on the bottom plate; the motor seat is used for fixing and clamping the motor; the to-be-mounted worm pushed in the bottom of a motor shaft is built in the motor in advance; after the motor shaft of the motor is pushed in the worm, thread rolling is performed; the cylinder is connected with the linear bearing plate through a connecting unit; the supporting shaft is mounted on the shaft bracket; the supporting shaft is parallel to the motor shaft of the motor; the linear bearing plate vertically sleeves the supporting shaft; and a limiting groove used for fixing and clamping the worm is formed in the middle of the linear bearing plate. The automatic pull-in mounting device can realize the automatic pull-in of the motor and the worm, and can reduce the labor intensity of a worker. Theinvention also discloses the automatic pull-in mounting method.