Abstract: When gas turbine works, rotational speed is affected by oil, air and so on, and there are strong cross-coupling between these factors. It is difficult to found an accurate mathematical model for the working process of gas turbine, so, the rotational speed of gas turbine can not be controlled by classical control theory. For the control problem of rotational speed of gas turbine, a useful self-optimizing fuzzy-PI control scheme is presented. According to fuzzy inference synthetize rule, the fuzzy control result is obtained. The fuzzy control result is used to control practical system and has met with success.