To solve the problem of the fractional of the laser energy absorption in solid output windows of conventional gas lasers, the free-vortex aerodynamic window is designed based on the aerodynamic theory and numerical simulation, The position and width of the diffuser＇s intake are studied by means of numerical simulation of the overall flow field in this paper. The appropriate width and position are obtained. At last, the overall flow of the free-vortex aerodynamic window is calculated and discussed using the finite element method, the calculation results show that the design is reasonable.