Under power market, distributed energy storage (DES) can participate in market transaction and make use of price fluctuation. However, individually accessing every DES to the power dispatch center results in the problem of high cost and low efficiency. Therefore, this paper proposes that the control strategy of distributed energy storage participating in power market transaction. First, an aggregation group is formed by aggregating distributed energy storage. On this basis, the conditional value at risk (CVaR) method is introduced to quantify the income risk brought by the fluctuation of power spot prices, and the regulation model in the day-ahead market of the DES aggregation group with consideration of the income risk is proposed. Finally, case studies are conducted to verify the effeteness of the proposed model. The control strategy can effectively guarantee the economic profits of the DES aggregation group compared to the peak and trough flat power prices.