Abstract: To solve the problem of strong fluctuation of load power in port shore power system, a load power flexible control method based on energy storage battery is proposed, on the basis of realizing real-time power suppression and dynamic reactive power compensation, which reduces system network loss, improves the cycle life of energy storage battery and enhance the ability to cope with extreme working condition. The topology and control method of load power flexible control system are introduced first. The working conditions of load are then divided according to the load power and state of charge of battery. According to the requirements of suppressing load power fluctuation, preventing battery overcharge and overdischarge and improving the ability to cope with extreme working condition, the working modes of load power flexible control system are divided into idle, valley fill, peak cut and limiting modes. Moreover, the system network loss optimization model is established, the reference interval of the power compensation reference is obtained through solving the model, and the power compensation reference of load power flexible control system under different working conditions is determined based on the reference interval. Finally, based on the measured load data of a shore power system on the Yangtze River, the working performance of load power flexible control system is verified by the simulation and experiment. The results show that the compensation response time of load power flexible control system is less than 0.3 s, the suppression rate of load power fluctuation reaches 90%, and the system network loss rate decreased by 17.2%.