Abstract: Supercritical carbon dioxide (SCO₂) Brayton cycle is a highly promising energy conversion process. Dry gas seals with low leakage rate employed as SCO₂ compressor and turbine shaft-end seal can significantly improve system efficiency. However, the high pressure, high speed and unconventional properties of CO₂ near the critical point still make it a challenging task for performance prediction of a dry gas seal. A numerical model for steady-state performance considering the effects of real gas, choked flow and turbulence in a SCO₂ dry gas seal was established. The influences of various effects on opening force and leakage rate of a SCO₂ dry gas seal were investigated under different working conditions. The results show that both turbulence and real gas effects have a significant influence on the steady-state performance of a SCO₂ dry gas seal, and the influence of choked flow effect is the lowest. The turbulence effect makes the tendency of opening force varied with rotating speed completely different from that predicted by laminar model, which is the result of combined action of turbulence effect on static pressure force and dynamic pressure force.