A PIV experimental study of flow structures of synthetic jet arrays which had different orifice spacing was carried out. To capture the instantaneous flow velocity vectors
the phase-locked technique was designed for the experimental system. The experiment images show the complete forming process of single jet synthesized by the interaction of vortex rings produced by twin synthetic jet respectively. It is found that the spatial distance needed for synthesizing is varied with the spacing of the jet arrays. It is similar to the conventional 2-D jet that the cross-velocity profiles at different stations after the synthesizing position are self-simulation. The property is also suitable for the lateral sides of jet arrays in the synthesizing distance.