There are many applications of the synthetic jets, such as separation
control, flight control, enhancing mixing, vectoring thrust, noise control, etc.The advantage of synthetic jets is zero-net-mass flux (ZNMF) which does not require a complex support system. Therefore, synthetic jet has become an important research topic on the active flow control. This study aims to numerically study the synthetic jet by using a parallel unstructured Navier-Stokes flow solver. The main purpose of this work is to investigate the effects of the important parameters for the gas dynamics of synthetic jet,such as the frequency of oscillation, inlet velocity, and the aspect ratio of the orifice. Besides, a comparison of 2D and 3D computational results and the mechanism of vortex generation are also included.