The model of the free vortex aerodynamic window with high pressure-ratio was established, and the whole flow field of the aerodynamic window was simulated. The result shows that there is no obvious wave through the export channel of the laser; with the contour of the free-vortex nozzle optimized, the shock wave behind the output of the free vortex nozzle disappeared, and the free-vortex jet flow field get better; with the boundary flow of the diffuser optimized, the total energy of the jet is heightened. The sealing pressure of the aerodynamic window is reduced from 37.5torr to 6torr. The results do effort to the free-vortex aerodynamic window′s research and development.