Abstract: Dynamic responses of a wind turbine to sudden wind speed changes are usually hysteretic because of the wind’s stochastic characteristics and large moment of inertia in the rotor, which may cause large fluctuation of rotor speed and output power. Based on linear quadratic Gaussian(LQG) control theory, an optimum pitch control is proposed, which could inhibit the rotor speed and power fluctuations better than traditional PI control. With a wind turbine of 2 MW as a research object, a simulation analysis of LQG and PI controls is conducted by using FAST-MATLAB/Simulink joint software platform, which shows that the optimum pitch control based on LQG theory could effectively reduce the fluctuations of speed and power.