Abstract: In the simple PID control in ordering machine, the temperature of hot air was controlled by an cool/hot air valve while kept the membrane valve setting unchanged, which resulted in fast temperature rising, unsteady control system, long adjusting time, large over regulation and low control precision, and it is not easy to keep the temperature variation of ordered tobacco within the specified limitations of ±1℃ The concepts of self-adaptive control, optimal control and predictive control were introduced into traditional PID algorithm. The improved PID algorithm was applied to control the temperature of ordering machine in primary processing line. The practical operation showed that the improved controller featured fast response, low over regulation, and no system oscillation. The control system was stable, and the control precision of temperature could reach ±1℃.