Abstract: The aerodynamic characteristics of delta wings is dominated by the leading edge vortex. Using flow solver TRIP2.0(Trisonic Platform version 2.0), the generation and evolution of vortex structure from the leading edge of a delta wing for different transonic free stream conditions are studied, and the comparision with force measurent are presented also. Structure multiblock mesh, LU_SGS solving method, highorder TVD scheme and SST turbulent models are selected to simulate the complicated flow field. Mutigrid technique is used to accelerate convergence speed. The generation, evolution and breakdown of the vortex and its influence on aerodynamic characteristics are analyzed for various parameters including Mach number, angle of attack and angle of sideslip .Numerical results show that the breakdown of subsonic vortex occurs in negative pressure region, and it starts from the vortex axis. It is not easy for a supersonic vortex to breakdown, except that the vortex is changed to a subsonic one due to a shock wave. The vortex structure under typical angle of sideslip is studied carefully, some valuable conclusions are obtained.