Abstract: Unstable operation of a hydro-turbine governing system causes its power units to loss safety and stability. The increasing demands for stability is often in conflict with difficulties in practical operation control. This study has focused on the stability control of such a system. First, a whole nonlinear model of a hydro-turbine governing system was developed by using a modular approach, the simulation showed that the system was unstable. Then, based on the Lyapunov stability theorem and finite time control theory, a terminal sliding mode control method was proposed to avoid the singularity of traditional terminal sliding surface, and a hydro-turbine governor was designed to eliminate the unstablity of the system based on the method. Finally, Matlab simulations verified the effectiveness and rapid response of the hydro-turbine governor. This study would provide a useful reference for stability control of actual hydropower units.