Abstract: Development of grid-scale energy storage is an important access to meet the growing demand for electricity arising, electric energy time shift, and the grid integration of high penetrations of renewable energy. Energy storage applications in grid will significantly improve the security of grid operation, reliability, economy and flexibility. In this paper several energy storage technology types suitable for grid-scale development are described, and a comparative analysis of the advantages and disadvantages of these energy storage technologies are made, the factors that influence the grid-scale energy storage applications are pointed out. Five grid-scale energy storage applications that have the greatest overall potential to benefit power system planning and operations are analyzed include of frequency regulation, renewables grid integration, transmission and distribution upgrade deferral and substitution, load following, and electric energy time shift. Through analyzing these applications, some storage technologies certain economic, technical performance, and design targets in order to optimize grid functionality are given out. Finally, some problems and challenges are presented in the development of grid-scale energy storage applications need to be addressed, and a guidance to the energy storage technology research and industrial development is provided.