A high proportion of renewable energy system needs appropriate energy storage to reduce its uncertainty, however, most of the existing energy storage configuration methods rely on off-line or simulation technology, which has the shortcomings of high calculation cost and low efficiency, and is difficult to meet the real-time scheduling requirements of complex and variable novel power system. To solve this problem, a new system inertia support energy storage configuration method based on analytical method is proposed. In order to fully represent the uncertain effects of renewable energy and traditional generators on system inertia, the system equivalent probability distribution model is established, to solve the expected power generation and synchronization probability of traditional generators. Synchronization probability model of renewable energy represented by wind farm is established. Expected inertia of system is solved on this basis. The demand inertia is solved according to RoCoF constraints, and the energy storage configuration is designed and realized through the missing value of the system inertia. The proposed method is verified in an IEEE 39 node system, results show the effectiveness of the proposed method.