The wavelength of semi-conductor laser diode(LD)varies with the temperature. Meanwhile,the output power also drifts according to the temperature and the used time. Therefore,it is quite necessary to control the temperature of semi-conductor LD. Concerning the characteristics of thermostat controller for LD,the theories of PID control and fuzzy control were analyzed. By combing SIMULINK2.1 and FuzzylogicTool-box,the computer simulation design for the self tuning PID parameters control system was implemented. The result shows that this method is simple and easy to operate and can be applied to some other small-sized temperature control systems as well.