Abstract: Numerical simulation was used to simulate the turbofan engine performance under afterburning condition.The volume effect of the mixer,afterburner,main combustor and fan duct as well as the variation of the nozzle area was considered.Based on the developed simulation model,the influence of nozzle critical area change on engine performance under afterburning condition was calculated.The results are consistent with the experimental data.The simulation model can lay an academic foundation for evaluating the effect of nozzle area control.