After the carbon neutral target is proposed, China’s new energy will usher in a leapfrog development, and its volatility and randomness put forward higher requirements for the flexibility of the power system. Energy storage has strong flexible adjustment capabilities. With the continuous improvement of technology and economy in recent years, it has been promoted and applied in all aspects of the power system, and its value in improving system flexibility is gradually reflected. This paper satisfy the power balance system and new energy given perspective, aiming at the lowest cost of power supply, regional energy storage size optimization model is put forward, with a actual regional power grid as an example, has carried out empirical research, quantitative analysis of correlation between the development of new energy and energy storage scale and verify the model is scientific and accurate.