Abstract: Electrochemical energy storage responds to tie-line power deviation in seconds, while the indexes CPS1 and CPS2 that measure the tie-line power deviation are computed by the cumulative value of tie-line power deviation in minutes, thus making it hard to objectively evaluate the contribution of energy storage to frequency regulation. To this end, a method is proposed to evaluate the contribution of electrochemical energy storage participating in the frequency regulation auxiliary service market. In this method, the “area control error” is used as an influencing variable to indicate the frequency regulation effect of energy storage power stations, and a correlation is established between “frequency regulation power of energy storage power station” and “area control error” to obtain the effect value of energy storage frequency regulation on area control error, eventually constructing an index to measure the frequency regulation contribution of energy storage. Based on the confidence level, the distribution of frequency regulation contribution index of energy storage is analyze to determine the contribution and economic benefits of energy storage in the frequency regulation market. The proposed method is verified through the actual operation data of a provincial power grid, which shows that the proposed method can accurately measure the frequency regulation contribution of energy storage, providing a reference for reasonably formulating the mechanism of energy storage participating in frequency regulation auxiliary service.