The opening and closing of the lead blade of the electric X-ray Collimator is usually driven by a miniature DC motor. The irradiation field can be adjusted to the required size by properly controlling the forward and reverse rotation and operation time of the DC motor. The adjustment of the irradiation field of the electric X-ray Collimator is not only carried out on the X-ray Collimator, but also controlled on the operating table beside the bed. In addition to the continuous adjustment, the latter has various fixed size selection buttons for the irradiation field. As long as these buttons are pressed, the motor drives the lead leaf to move to the selected irradiation field and fixes it to meet the specific requirements of photography. The motor is operated with automatic limit protection of limit switch in the position of lead leaf closing and maximum opening.