A computational study was conducted to investigate the effect of nozzle pressure ratio on flow filed and performance in a fluidic thrust vectoring nozzle. The results indicate that with the increase of nozzle pressure ratio, the thrust vector angle decreases. The shock wave in front of injection moves downstream, therefore the pressure difference of upper and lower wall decreases, and thrust vector angle decreases; With the separated flow region pressure of injection downstream decreases, the pressure difference of upper and lower wall decreases, thus thrust vector angle reduces; With operational condition changes, the difference between thrust vector angle and flow deflection angle increases, and the thrust vector angle decreases.