Equipped with various protection devices, the gantry cranes of Aicrane have the highest safety. One of these protection devices is the monitor system on the overload limiter, which warn operator the overload situation by a display screen timely. Next is the self-examination, all the directors can test themselves in a gantry crane through this system, mainly includes the working condition of voltage and button. Finally is the upper and lower limit switches, when the hook approach to the limit height of a gantry crane, these switches will cut the electric automatically, leaving the motor don’t work or move to the opposite direction.