As a new type of active control technology, plasma synthetic jet (PSJ) is designed to object the poor robustness of traditional synthetic jet technology. The software is Fluent6.3 and the grids for numerical simulation are structure. The flow field surrounding the PSJ device was simulated numerically to get the evolution regularity of the flow field. The affection on the velocity of the device exit was compared between different discharge durations. The results show that the PSJ device can generate high speed jet which enlarges the instability of flow. The high velocity 439m/s is achieved. It is also suggested that the longer the discharge duration, the higher the speed of the device exit. And it can be used for high speed flow control.