The temperature control system needs to have high accuracy and stability for many optoelectronic applications.In this paper,based on C8051F021 microcontroller,the PID control algorithm is improved and the temperature control system of the high power semiconductor laser is designed to solve the problems of long time,low precision and poor stability of the traditional temperature control system.The experimental results show that the precision of the temperature control is up to ±0.1 ℃.