Abstract: In order to optimize the design of hydrogen turbo-expander based on the mean-line model, a genetic algorithm (GA) was used to obtain the design parameters under optimal performance. The effects of critical parameters such as flow coefficient, load coefficient, mass flow rate and rotational speed on the performance of hydrogen turbine expander were investigated. Results show that the efficiency of the hydrogen turbo-expander is improved by 3.08% after adopting the optimal design parameters. The variation of mass flow rate and rotational speed has significant influence on hydrogen turbo-expander efficiency. Under the optimal turbo-expander geometry, when the mass flow rate is in the range of 0 to 0.5 kg/s, the efficiency of the hydrogen turbo-expander is above 70%, which can realize efficient operation of the hydrogen turbo-expander.