Abstract: Reversible solid oxide cell (RSOC) is a device with both power generation and hydrogen production capacities. The current density overshoot in the transient of power generation - hydrogen production mode switching process has adverse effects on RSOC life and energy conversion efficiency. However, there are few researches on RSOC mode switcing transient characteristics and current overshoot. Thus, we study and deeply analyze the overshoot phenomena during the mode switching period based on the multi-physics coupling RSOC model. We find that increasing the mole fraction of H₂O at the inlet of fuel channel can decrease the overshoot from fuel cell (FC) mode to electrolysis cell (EC) mode and increase the overshoot in the opposite switching direction. In addition, under the research of different mode switching ways, the relationship between the current density overshoot and voltage variation is not completely positive. The research will provide a theoretical basis for the reliable operation of RSOC equipment in the electro-hydrogen coupling energy system in the future.