Abstract: Supercritical carbon dioxide (S-CO₂) Brayton cycle power generation technology has multiple advantages and huge potential for future applications. S-CO₂ turbomachinery generally uses dry gas seals with extremely low leakage, but the special physical properties of S-CO₂ have a significant influence on the steady-state performance of dry gas seals. Currently, the research on the performance of S-CO₂ dry gas seals is mainly based on theoretical simulation, with little experimental research support. To study the steady-state performance of S-CO₂ dry gas seal under different operating conditions, a high-speed and high-pressure dry gas seal test-rig is established. The effects of rotating speeds, inlet pressure and inlet temperature on the gas leakage and friction loss of the seal are studied. And the theoretically predicted results are compared to the experimental results. The results show that the leakage and friction loss of S-CO₂ dry gas seal increase at the higher rotating speed and the higher pressure, and decrease at the lower temperature. The influence of rotational speed and pressure is greater, while the influence of temperature is smaller. There is a certain deviation between the calculated leakage value and the experimental value, with a maximum deviation of around 20 %. The experimental results provide a reference for the correction of theoretical models and design methods for S-CO₂ dry gas seals, so as to further analyze the sealing performance of S-CO₂ dry gas seals.