Abstract: The return braking capacity of marine steam power devices is the fundamental guarantee of the emergency braking ability of steam-powered ships, and the torsional stress model of the rear journal of the high and low pressure rotors under the return steam braking condition is established by analyzing the working process of high and low pressure rotors under the changing working conditions of return steam braking, and the Simulink simulation model of torsional stress at the rear journal of high and low pressure rotors is established by using simulation software. Simulation shows that in the process of steam return braking of the steam power unit, when the perfect steam intake strategy of the forward and reverse steam turbines is adopted, the torsional stress at the journal at the rear end of the low-pressure rotor exceeds the safe allowable value, resulting in the reduction of the rotor service life or even fracture.The analysis of torsional stress of rotor during the return braking of marine steam power devices can lay a foundation for the optimization of steam braking control strategies for steam-powered ships and provide reference for improving ship maneuverability.