Abstract: A self-tuning PID control strategy is adopted for the temperature control problem with long time delays. First, the recursive least square method is used with a forgetting factor to identify on line the unknown characteristic parameters of the model. Then, a self-tuning PID control law is designed. The simulation results show that this method can accurately identify the characteristic parameters of the model and the self-tuning PID approach boasts faster response and smaller overshoot than the conventional PID control method.