Abstract: Edge-tone is a complex fluid dynamic phenomenon. The paper researches the edge-tone phenomenon by numerical simulation which is conducted under the condition of the jet instability, but below turbulence. The distributions of vortex, velocity and pressure as well as the characteristics of the reed at different fluid speeds are studied. Simulation results show that the vortex street and pressure are alternately distributed on both sides of the reeds and the fluid is obviously shaking. Based on the phenomenon, the mechanism of vibrating reeds generating edge-tone is preliminarily discussed.