Energy storage can improve the transmission and distribution capacity of power grid and control the fluctuation of power frequency in solving the problems of instability and intermittence of renewable energy generation. Reasonable economic benefit model is the key to the development of energy storage. In order to clarify the reasonable economic benefit model and main influencing factors of energy storage system in the current electricity spot market environment and tap the potential of China's energy storage market, this paper analyzes its internal and external environment through strengths weakness opportunity threats (SWOT) analysis. On this basis, based on the analysis of the characteristics of energy storage participating in the auxiliary service market and the electricity spot market, the internal rate of return (IRR) model is adopted, and an energy storage system in Jiangsu province is taken as an example to study the quantification of the economic benefits of the energy storage system in the electricity spot market. The economic benefits of the energy storage system in the spot electricity market are verified in several scenarios by building a model with the goal of maximizing economic benefits and solving it by using linear programming. Finally, from two different angles of technology and economy, the most important factors of current energy storage system economy are found through case study. The calculation results show that, from the technical point of view, the number of charge and discharge cycles is the main influencing factor; Based on policy pricing, the peak-valley price difference level is the main influencing factor. With the progress of investment cost and technical level of energy storage system in China, energy storage system will have stronger and stronger economic benefits under the background of full liberalization of power spot market.