The accuracy and stability of semiconductor laser’s output are greatly affected by temperature, temperature change will lead to the change of threshold current, electro-optic conversion efficiency and wavelength, and then affect the output power of semiconductor laser. As such, we designed a temperature control system for the normal operation of the semiconductor lasers at set temperature. This system uses a single chip microcomputer as the core control element, a thermoelectric cooler and a PTC heater as the executive elements, an AD590 temperature sensor and a PT1000 platinum resistor as the temperature detection elements. It controls the temperature by outputting pulse width modulation waves with different duty cycles through the variable-domain fuzzy proportional-integral-derivative (PID) control algorithm. Through simulation analysis, this control algorithm can not only reduce the system overshoot, but also possesses strong robustness. Experimental results indicate that the system can achieve the required temperature control precision of ±0.1 ℃ in the range of -12 ℃ to 120 ℃ and reach the target temperature within 250 s.