Abstract: In order to understand the heat transfer characteristics of regenerative cooling in two dimensional plug nozzle,a computational model was established and numerical simulation was carried out.The flowfield and the heat transfer characteristics of plug nozzle at different ambient pressures were investigated. Nozzle flow was assumed to be frozen, and convective and radiative heat transfer from gas to solid wall was considered. Discretization of the governing equations was performed with two order upstream scheme, and radiative heat transfer equation was solved with Discrete Ordinates (DO) method.Absorption coefficient of water vapor was calculated by Leckner formula.The results show that heat transfer condition internal the nozzle is the worst,and should pay more attention.The heat transfer characteristics on plug surface varies with operating conditions.At sea level condition,heating of the plug is the worst,and with the increase of pressure ratio,it is lessened and at last keeps unchanged with ambient pressure.An unreasonable plug contour design can cause a very high temperature peak on it.