In order to determine the appropriate deflection angle θ which can substantially influence the flow field around the jet blast deflector ( JBD) ，the flow field was numerically simulated at different deflection angle by the fluid-solid conjugate heat transfer method． The results show that the effect of the JBD separation is marked and the devices around the JBD are protected effectively at the 45°deflection angle． At the 30°deflection angle，some hot exhaust that is separated by the JBD flow behind and has a bad effect on the devices behind the JBD． At the 60°and 75°deflection angles，the forward flow of the hot exhaust will affect the devices in front of the JBD． So the appropriate deflection angle θ is 45°．