Abstract: The inner and outer flow field,temperature field and gas concentration field models including the heat shield in the after burning room of a vectored nozzle were established and computed.The effect of the heat shield position on the inner wall,i.e.the heat shield and the nozzle wall,temperature distribution and the corresponding infrared characteristics was studied.The results show that the transonic flow field solution governed by the Navier-Stokes equations based on the density solver is successful.The wall temperature firstly decreases and then increases when the heat shield length(or position) covering the converging nozzle increases.There is an optimized heat shield position that makes the wall temperature reach the minimum value.Finally the infrared radiant intensity emited out of the nozzle outlet section was calculated using autor's proposed discrete net-radiation method.