A set of device is designed based on PC to realize the functions of traditional potentiostats in the phase analysis of galvano-chemistry. In the device, A/D and D/A conversion is used to measure the electrode potential and convert the voltage for output; specific program runs in the PC to regulate and control the system. The effect of the proportion factor KP on the control variation is researched through certain experiment. Two experiments, the control of electrolysis in constant potential and the determination of polarization curves, are designed to test and evaluate the effectiveness of the device. The experimental results show that the variation between the actual anode potential and the target potential could be controlled to below 1 mV if KP is set to an appropriate value.