Abstract: This paper is to investigate the coherent structures of two-dimensionatemporally evolving mixing layer by direct numerical simulation (DNS) of Navier-Stokes equations using pseudospectral method. To avoid imaging error, mapping function designed by Cain et al. is used here to transform the original infinite region to a finite domain.The approach explains numerically the important role of fundamental perturbation wave-and its subharmonic wave in the formation, development and interaction of coherent structur...