The invention belongs to the technical field of energy storage, and provides a device and method for managing an energy storage system on a client side. The device comprises authentication and registration equipment, and local management equipment, wherein the status of networking between the authentication and registration equipment and an energy storage cloud platform is acquired, and an authentication request and a registration request are sent to the energy storage cloud platform after energy storage system information and a digital signature are encrypted; and the local management equipment carries out PCS monitoring and BMS monitoring on the energy storage system to protect the energy storage system, controls the energy storage system to charge and discharge to inhibit system fluctuations, and controls the energy storage system to participate in power grid services. The device and method provided by the invention has the advantages that energy interaction between client-side stored energy and a power grid is achieved, so that the energy storage cloud platform can carry out access authentication and acquire information of a power grid integrated platform at an upper end, and the client-side stored energy can be managed and controlled at a lower end; and the various pieces of the equipment in the device have clearly defined functions and can be conveniently maintained.