Abstract: Thermoelectric cooler(TEC) behaves approximately as a two-pole system,acting as the most important component to regulate operating temperature of the laser diode(LD).In order to research the influence of thermoelectric cooler module on stability of a temperature control system for a laser diode module,an analog proportional-integral-differential(PID) network was adopted as the system controller.By adjusting the PID control network,the response of TEC was optimized.For unit-step input,the stable state error and stability was studied.A conclusion can be made that the system takes on the better instantaneity and stability.