The 3~5um Medium Wave Infrared(MWIR) laser has gained a lot of attention for its important application values in remote sensing, medical, military and many other fields. However, there are many technical difficulties to fabricate those kind lasers, and the performance of their output power stabilities remain to be improved. In a practical application, the MWIR’s output power will be instability when the temperature changes and the current varies. So a system of reducing MWIR power fluctuation should be established. In this paper, a photoelectric system of stabilizing the output power of He-Ne laser is developed, which is designed based on the theory of feedback control. Some primary devices and technologies are presented and the functions of each module are described in detail. Among of those, an auxiliary visible light path is designed to aid to adjust WMIR optical system. A converging lens as spatial filter is employed to eliminate stray light well. Dewar temperature control equipment is also used to reduce circuit noise in IR detector. The power supply of AD conversion circuit is independently designed to avoid the crosstalk caused by the analog section and digital section. Then the system has the advantages of good controllability, stability and high precision after above designation. Finally, the measurement precision of the system is also analyzed and verified.