Three-dimensional incompressible boundary layer on a flat plate was studied where disturbance N-Sequation was taken as governing equation.The evolution of three-dimensional instability T-Swave was simulated by spatial DNS(direct numerical simulation) in which third-order precision mixed explicit-implicit scheme was employed for temporal discretization while a method combining Fourier pseudo-spectral method with high precision compact finite difference was implemented for spatial discretization.Acoordinate transform of nonuniform meshes was applied in normal direction

fringe method was adopted as exit boundary condition and MPImethod was used in programming.Through a simple case

the results obtained by this method were tested to be in consistence with the ones obtained with stability theory.