Numerical simulation methods of infrared characteristics of vectored nozzle in the spectrum range of 2 100～5 260 cm-1 are studied and corresponding Three Dimension (3-D) program was developed.The program can compute infrared characteristics of nozzle both in after-burning condition and non-after-burning condition.Spectral emission and absorption of water vapor and carbon dioxide

and soot after-burning condition were also considered in computation.The simulated results of axial-symmetrical vectored nozzle on wall and in the exit plane in after-burning condition and non-after-burning condition in the spectrum range of 2 100～5 260 cm-1 are presented in the paper.The numerical calculation results obtained by applying the present simulation approach to a real engine show general agreement with the experiments.