Abstract: Based on the theory of flow instability and coherent structure,a new theoretical 2-D wave model of the large eddy structures in the near wake region behind an airfoil was proposed.By calculation,we obtained the streamlines and the vorticity contours.They were in good agreement with those of experimental observations.Also the theoretical results of Reynolds Stress variation show good agreement with experimental results.It can be concluded that this model can depict the physical mechanism of the large-scale eddy structures in the near wake region.