This paper uses large eddy simulation (LES) to investigate Co-Flow Jet (CFJ) airfoil flows at high angle of attack (AOA). The standard Smagorinsky model with Van Driest damping is employed to resolve the subgrid scale stress. The 5th order WENO scheme is used for the reconstruction of the inviscid flux and the 4th order central differencing for the viscous flux. The momentum coefficient(Cμ) is chosen as a parameter to control the jet flow of the CFJ airfoil. LES simulations were carried out for the different momentum coefficients. The LES results at 30° AOA are compared with the experiment to understand the flow structure of the jet mixing and flow separation. The numerically captured qualitative flow structures are very similar to those obtained in experiment. The quantitative prediction of lift and drag agree very well with experiment.