The invention relates to an automatic assembly machine for rotor semi-finished products. The automatic assembly machine comprises a machine frame and a power distribution control box. Two conveying devices matched with a rotor shell are arranged on the machine frame, and an overturning device is arranged between the two conveying devices. The left conveying device is provided with a shell sealingdevice and a spooling device which are matched with the rotor shell. The right conveying device is provided with a shaft sealing device, a bearing assembly device and a stacking plate tray assembly device which are matched with the rotor shell. The overturning device comprises an overturning movable cylinder arranged on the machine frame, and the overturning movable cylinder is connected with an overturning movable block. An overturning pneumatic motor is arranged on the overturning movable block, and is connected with an overturning clamping cylinder, and the overturning clamping cylinder isconnected with an overturning clamping block matched with the rotor shell. According to the automatic assembly machine, the rotor shell is conveyed by two separated conveying devices, the overturningdevice is mounted at the butted joint position of the two conveying devices, the integrated assembly of a rotor bearing is achieved, and the assembly efficiency is greatly improved.