Wind power prediction has important significance for wind farms and the stable operation of power system. Wind power prediction accuracy can be improved by raising wind speed prediction accuracy. wind on the wind farm is not always effective vertical role on the fan, the wind direction on behalf of the angle between the wind speed and fan, which determines the vertical effect of effective wind speed on the fan, so the direction of the wind is one factor affecting wind power prediction accuracy. This artical analyzed the wind direction space dispersion and the mechanism of wind power calculation and prediction error, the mechanism of the mutual relations between all kinds of error is given. Numerical example results show that considering the wind direction spatial dispersion is more effective than only in terms of average wind direction. Examples show that considering the wind direction spatial dispersion based on the wind speed spatial dispersion will further improve the whole wind power prediction accuracy.