Objective To provide Laser generator with a precision constant-temperature environment.Method This system was developed on the bases of PT100 sensor circuit,MCU and SSR.The inputting PT100 voltage was first amplified and deflected,and then delivered to AD650 to perform V/F.The outputting frequency was measured with high precision by T0 port of MCU C8051F020,and the micro-controller calculated the result and transmitted PID output signal by 16 bit PWM to heater.Results This precision constant-temperature water circulator was gifted with an error within ?0.05℃.Conclusion This precision constant-temperature water circulator can make an ideal temperature environment available for laser generator.