Abstract:  In this paper, an experimental supercritical CO2 critical flow investigation was carried out. The effect of upstream stagnation parameters and length to diameter ratio on the critical flow rate was obtained. A prediction correlation of mass flow rate equation was proposed based on the experimental data. The comparisons of correlation prediction and experimental data from open literature show good agreement. The deviation is within the boundary of ±15%. It shows that the present correlation can predict the supercritical CO2 critical flow rate.