The forecast accuracy of wind power based on the meteorological wind speed data can not satisfy the real project demand. Based on the principle of energy conservation， a new concept of equivalent average wind speed is proposed. The relationship between the equivalent average wind speed， the mean and maximum wind speeds is built through an analysis on the one-year spot experiment samples. A forecast method of wind power based on the equivalent average wind speed model is presented. A forecast results comparison shows that the proposed method significantly improves forecasting precision.