Abstract: The purpose of starting the spot market is to establish a market-based power balance mechanism that combines medium and long-term power transactions with spot transactions. In the early construction stage in which the market operation mechanism is not perfect， the short-term assessment mechanism with a daily settlement period is conducive to fair market transactions and stabilize power fluctuations in the spot market. With the objective of intuitively reflecting the impact of short-term deviation power assessment on the revenue and business strategy of the electricity retailer， a revenue model in day-ahead market of the retailer that takes into account the daily deviation power assessment mechanism is constructed. On the basis of real-time market purchase and electricity trading with energy storage stations a daily deviation power assessment optimization model with the objective of maximizing revenue of retailer is established. According to the 2017 transaction data of Guangdong Power Market， the typical daily spot transaction and actual power consumption are simulated. Moreover， sensitivity analysis of uniform clearing price， unit assessment cost， transaction price with the energy storage station and positive and negative deviation is conducted. The results show that the optimization strategy can significantly improve the revenue of the retailer；uniform clearing price， unit assessment cost and the prices of electricity purchased from the energy storage station have the greatest impact on the additional cost；the prices of electricity sold to energy storage power stations have the greatest impact on additional revenue；positive and negative deviations have the greatest impact on the overall revenue of the retailer.

Key words: spot market, deviation penalty, energy storage power station, electricity trading, sensitivity analysis