Abstract: Condensation on the containment structures during an accident is one of the critical thermal-hydraulic phenomena that would affect the pressure in the containment vessel. Experiment facility was set up to investigate the steam condensation with non condensable gas on a cold plate,focusing on the conditions in the containment. In the experiment, pressure range is 0.11 ~ 0.5 MPa;mass fraction of air in the bulk flow is 29%~78%; the wall sub-cooling is 26~60℃. Gas velocity varies from 0.4 to 1.9 m/s. The experimental result agrees with empirical correlations when the gas velocity is up to 0.9 m/s. Gas velocity becomes one of the primary factors influencing the steam condensation in non-condensable gas with higher gas velocity. The promotion effect on the heat transfer of increasing velocity is more significant when the mass fraction of non-condensable gas is lower. The transition criterion from free to mixed convection for steam-gas flow condensing should be different from that of the single phase heat transfer.