The high-frequency method for solving the scattering of electrically large coated targets in half space is presented in this paper. In order to consider the influence of environment, the half-space physico-optical integral equation is deduced by introducing the half-space Green's function into the physico-optical method. Combined with the graphical-electromagnetic computing method, the shadow regions are eliminated quickly and the geometry information is attained by reading the color and depth of each pixel. Meanwhile, we use the impedance boundary conditions to account for the target covered RAM in half space, and the radar cross section of coated targets can be exactly calculated in half space. The numerical results show that this method is efficient and accurate.