Closed feedback control to DC motor was made by PID based on SPMC75F2413A SMC and coder in order to make the hookliked scanning probe driven by the DC motor to rest on the specified position. The PID feedback control algorithm can be used to realize displacement control. The coder changes the displacement of the hookliked scanning probe to electric pulse. Through SPMC75F2413A SMC, these electric pulses were analyzed and compared to the specified value. The output signals were calculated by the differences to control the right and reverse round of the motor, i.e. when the hooklike probe is higher than the position, the DC motor rotates reversely immediately, if lower, the motor rounds rightly.