The parameters of large wind turbine need to be adjusted timely to avoid excessive wind energy that will cause damage on the wind turbine itself. Based on the simplified mathematical model of wind turbine, we got the relationship curve between its parameters. When the speed of wind was higher than the rated wind speed, we figure out the value of pitch angle during the changes of effective wind speed to keep rated output power. Neural Network used to train the data and pitch control system was built, it used to adjust pitch angle once the wind changes, and maintain the output power at rated value. The complex mathematical relation can be replaced by the trained network model. Detailed simulation results have confirmed the feasibility and performance of the optimal control strategy, which protect the wind turbine from damage and prolong its service life.