In order to cope with the challenge of randomness and volatility brought by large-scale renewable energy access to the power grid, and to ensure the flexibility of renewable energy utilization, it has become a hot topic to add reasonable energy storage equipment into the actual power grid operation. A load frequency control (LFC) strategy based on linear auto disturbance rejection technology is proposed. It can solve the problem of electrochemical energy storage participating in frequency modulation of interconnected power grid with pumped storage power station. Based on the establishment of a combined pumping/storage LFC model considering the dead zone of the governor, the power generation speed limit and the other nonlinear conditions, the performances of different controllers are compared, and a designed second-order linear active disturbance rejection controller (LADRC) is adopted, with its excellent control performance and the introduction of demand response (DR) to participate in frequency regulation. The simulation verifies that the system has stronger anti-interference ability after adding electrochemical energy storage to the pumped storage, and has a good dynamic response to smooth the frequency fluctuation of the power grid.