This paper proposes the cooperative fuzzy controller of AVR and GOV to improve the transient stability of power systems. The fuzzy rules to stabilize the power systems are selected from general ideas based on the sliding mode controller. The both AVR and GOV input are determined to satisfy system's stability from the values of state variables, acceleration power and magnitude of their products. Moreover, these control laws reduce chattering effect due to discontinuity of the control laws. Therefore, this fuzzy controller acts to improve the transient stability of power systems. By introducing the ideas of sliding mode control, the fuzzy rules and composition of membership functions can be constructed easily. The validity and usefulness of proposed fuzzy controller are tested on a single-machine infinite bus system. It is shown that the proposed controller has robustness regarding parameter errors in the synchronous machine and that the transient stability of power systems is improved by cooperative AVR and GOV control.