Active control of jet is applied at control of burner flame or air conditioning. In this study, secondary film flow is built on the outside of axisymmetric jet. And it is driven by the acoustic excitation for active jet control. Furthermore, the velocity ratios of mainstream and film flow and acoustic strouhal number were changed. The freestream velocities were measured by the LDV and jets were visualized by LLS for research of change in jet structure. As a result, axisymmetric jet is diffused in all condition by acoustic excitation vortices. In the case of VR=0.5, potential core is shortened by St=0.6. At VR=1.0 diffuses than at VR=0.5. Potential core is most short at VR=1.0, St = 0.6. Mainstream most mixes with film flow at VR=1.0, St=0.6 and film flow mixes with surrounding air at VR=1.0, St=0.3.
