Abstract: The performance of the cooling air flow extracted from the bypass duct to cool a new fuel injector with double-wall construction for afterburner was simulated numerically.The results of the simulation and the experiment agree with each other very well.The temperature distribution of outer casing and inner pipe, and cooling air rate extracted from the bypass duct were obtained by calculations under four working conditions of the afterburner.It shows that the type of afterburner fuel injector can extract enough cooling air from the fan stream and can effectively decrease the temperature of the wall of fuel injector.