Abstract: The hydrogen turboexpanders are critical component in large-scale hydrogen liquefiers. In order to investigate its performance, this study designs an experimental system for testing cryogenic hydrogen turbine expanders operating from ambient to liquid hydrogen temperature ranges. The core objective of this system design is to facilitate the expansion refrigeration process within hydrogen liquefaction equipment and to analyze both the thermodynamic and mechanical performance of the hydrogen turboexpander. Thermodynamic performance testing includes adiabatic efficiency, actual refrigeration capacity, and expansion ratio, serving to evaluate the turboexpander's efficiency. Mechanical performance testing encompasses continuous maintenance-free operation time and start-stop frequency, assessing the reliability and lifespan of the hydrogen turboexpander. Additionally, error analysis during the testing process is conducted. This experimental system serves as a testing platform for evaluating the performance of cryogenic hydrogen turboexpanders, enabling the acquisition of key technical parameters and facilitating optimization to further enhance the performance of both hydrogen turboexpander units and hydrogen liquefaction processes.