Many numerical and experimental researches have been done for the flow around oscillating airfoils. The main research topics are wake vortex shading, dynamic stall phenomenon, MAVs lift and thrust generation, et.al. Until now, researches mainly have been concentrated to analyze the wake flow for the variation of frequency and amplitude at a low angle of attack. In this study, wake structures and acoustic wave propagation characteristics were studied for pure harmonic plunging oscillating airfoil at a high angle of attack. The governing equations are the Navier-Stokes equation with LES turbulence model. OHOC (Optimized High-Order Compact) scheme and 4th order Runge-Kutta methods were used. The Mach number is 0.3,the Reynolds number is 1.0×10<SUP>5</SUP>,and the angle of attacks are 20° ~ 50°. The plunging frequency and the amplitude are from 0.05 to 0.15, and 0.1?0.2, respectively. Because of the high resolution numerical methods, wake vortex shedding and pressure wave propagation process, as well as the propagation characteristics of acoustic waves can be simulated. The results of frequency analysis show that the flow has the mixed characteristics of the forced plunging frequency and the nature vortex shedding frequency at a higt angle of attack.