Large eddy simulations are conducted to investigate the coherent structures of a two-dimensional supersonic mixing layer.The Governing equations of large scale eddies are solved with fifth-order WENO scheme and the effect of small scale eddies is simulated with Smagorinsky subgrid scale model.The results show that the development procedure of large structures and reveal the behavior of large eddies.Frequency spectrum analysis of the unsteady pressure data is performed to investigate the acoustic characteristics of different streamwise location in the mixing layer.Time-averaged velocity profiles obtained from the simulation are consistent with the experimental data.