A high precision temperature control system of excimer laser was proposed. The system can sample the temperature of the chamber of excimer laser in real time, and then display and control it. So the constant temperature of excimer laser chamber can be achieved which can improve the working performance of the excimer such as energy stability and working life. The system used Freescale chip as controller, and proportional valve as its executive component. Meanwhile, the software, hardware and optimization control algorithm were designed. Experimental results show that under the three different PID control ways, the control precision of the system is ±0.2°C. Under the improved intelligent control, system overshoot is smaller and response time is reduced. At the pulse rate of 100 Hz and 500 Hz, the system can run steadily. So the system can provide a favorable temperature environment for the laser’s operation.