Although the jet blast deflector (JBD) can change the direction of the engine wake to the upward, and prevent the deck from being ablated and protected the equipment behind the aircraft, the backflow generated from JBD is unfavorable to the engine. In this paper, the characteristics of the backflow based on the vertical angle of 0°, 2°, 4°, 6°, 8°, 10°and 12° are investigated. The results indicate that the backflow would change the direction to the outward under the wake flow. If the JBD vertical angle is less than the critical angle 6°, the backflow would flow along the engine and be easily drawn into the air inlet. Or the backflow would remain changing direction to the outward, even to the backward, avoiding the backflow drawn into the air inlet. These are for reference of the layout only.