A high proportion access of renewable energy sources (RESs) enhances the characteristics of net power fluctuation and low inertia of the new power system. This brings greater challenges to frequency regulation and stability. Thus an improved dead zone frequency regulation control strategy for energy storage to meet the increasing frequency regulation demand is proposed. First, the frequency response model of a power system with an energy storage dead zone is introduced. The characteristics of system frequency varying with the increase of RESs penetration are analyzed, and the shortcomings of the traditional dead zone are elaborated. Then, an improved dead zone setting method based on frequency regulation stage division is proposed, where the frequency response modes are set according to the frequency changing status. Based on the description function method, the influence of dead zone nonlinear elements on the stability of the system is quantitatively analyzed, and the stable boundary of the droop coefficient considering the dead zone is given. In addition, a capacity configuration method is proposed for energy storage in frequency regulation. Finally, a regional power system model is built with an RESs farm, and the dynamics are compared with different dead zone settings. The simulation results verify that the proposed dead zone can effectively improve the frequency quality, relieve the frequency regulation burden, and will not increase the capacity configuration. It has a certain economic and practical value.