The invention discloses an electric energy quality steady-state index prediction method and system. The method includes the steps that monitored historical data within preset time periods are acquired; a time sequence algorithm is utilized to calculate the active power within prediction time periods according to the historical active power, and then the prediction active power is obtained; a regression analysis method is utilized to calculate electric energy quality state index data within the prediction time periods according to the prediction active power and the historical data, and then prediction electric energy quality steady-state index data are obtained. Due to the fact that the active power of a power grid is relatively steady, the time sequence algorithm is utilized to predict the active power within the prediction time periods according to the historical active power, and then the prediction active power is obtained; then, the regression analysis method is utilized to calculate and predict the electric energy quality state index data according to the prediction active power and the historical data. Therefore, accuracy is high, electric energy quality steady-state indexes can be effectively predicted, safe operation of the power grid is guaranteed, and the influence caused by electric energy quality problems is avoided.