Abstract: The flow field of planar jet is simulated by discrete vortex method. The rolling up, rotating and merging processes of large-scale vortex structures in the planar jet are displayed and the temporal and spatial evolution characteristics are disclosed by the simulation results. The instantaneous velocity at the fixed position and the mean velocity of the fluid field are computed. The results of time-averaged velocity simulation are in accordance with the values of the experiments and the unsteady and instable nonlinear characteristics of the large-scale coherent structures in the planar jet are displayed from the instantaneous velocity distributions.