A radiation inspection system includes a shielding door device for a radiation inspection system, comprising a door body, two guides located on two opposite sides of the door body, a rack, a gear and a motor. The two guides are fixed on an upper surface of a frame and the door body is movably connected to the two guides via bearings. The rack is fixed on a bottom of the door body and meshed with the gear. The gear is coupled with a shaft of the motor fixed on a lower surface of the frame. This configuration is advantageous in automatic and complete shielding of the radiation inspection system without interference. In addition the shielding door can be controlled intelligently, so that accidental radiation leakage can be prevented.