A high proportion of renewable energy system needs appropriate energy storage to reduce its uncertainty, but most of the existing energy storage configuration methods rely on off-line or simulation computing technology, which has high calculation cost and low efficiency. To solve this problem, a new 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 equivalent load probability distribution model considering load, generator outage capacity and the renewable energy unit outage capacity was established firstly, to solving the expected power generation and synchronization probability of traditional generators. Synchronization probability model represented by wind farm was established as well. Expected inertia of system was solved on this basis. Then, by solving the expected inertia and minimum demand inertia of the system, the energy storage configuration of high proportion renewable energy system is realized. Finally, the proposed method is verified in an IEEE 39 node system, results show the effectiveness of the proposed method.