A battery energy storage system (BESS) control method based on time-varying intersection of the dual targets is proposed to suppress the random fluctuation of wind power and improve the accuracy of ultra short-term prediction of wind power. Firstly, a respective single control limit, intersection combined control limit and further time-varying intersection combined control limit once different time-scale of the dual control targets is considered are established. On this basis, combined with the operating constraints of the energy storage, the final control strategy of battery energy storage to improve the wind farm output is arrived at. Secondly, valuation and forecast accuracy assessment metrics based on off-limit probability and off-limit relative mean value is set up and comprehensive evaluation system of the dual targets is developed. Finally, by applying the real output data of a wind farm, on the premise of using neural network time series model or ARIMA model, three size relations of tolerance of wind fluctuation and tolerance of ultra short-term prediction error is considered to verify the effectiveness of the control strategy by calculating the total variation and RMSE and meanwhile both suppress random fluctuation and improve the ultra short-term prediction accuracy of wind power. This work is supported by National Natural Science Foundation of China (No. 51267020).