In view of the research on the process of ship load transfer in the shore power of the inland river basins, in order to suppress the reverse power and load fluctuations caused by directly cutting off the ship''s diesel power system after grid connection, a step-by-step power switching control solution based on load transfer from ship power to shore power is proposed. By analyzing the power fluctuation phenomenon in the process of shore power load transfer, the conditions of step-by-step switching based on power overshoot and dynamic response time are given. Based on the power quality index of the ship''s side load, the output power of the ship''s synchronous motor is under step-by-step control to reduce the negative impact of power fluctuation and load frequency offset, also improve the quality of power supply. Build a shore power simulation platform by Simulink to study the advantages and disadvantages of power step-by-step switching control and existing strategies. The simulation results show that the proposed strategy is correct and effective. It can achieve the smooth transition of load after grid connection.