To reduce the effect of mechanical and electrical disturbance on torsional vibration of steam-turbine generator shafting, in a single machine infinite system, a six order nonlinear state space model is set up for steam turbine generator shafting based on the generator excitation and speed-regulation system. According to the accurate feedback linearization theory, the multi-index nonlinear coordination (MINC) control strategy is designed for suppressing the torsional vibration of shafting. The strategy is compared with linear optimal control (LOC) method. The simulation results show that when the short-circuit fault occurs and the regulating power and voltage are disturbed, the MINC method can restrain oscillation of the angular displacement deviation between turbine and generator, reduce the risk of shaft torsional vibration, give better consideration of both dynamic and static performance of each state quantity, and stabilize the operation of power system.