This article is researched on the system of intelligent control of water temperature which controlled by SCM based on the STM32. This system has high-precision, it is using the algorithm combined the control in sections and confirm the parameters of PID. The temperature under the control of phase-angle of controllable-Si conductivity when we need to higher it, and using the technology of PWM to lower it. Results show that the system has high precision in both static and dynamic, low volatility in coefficient and excellent stability in performance.