Abstract: Based on traditional shooting and bouncing rays (SBR), the ray-tracing procedure and intersection tests were improved for the flat surface scatterers. Combined with SBR, a fast method of ray/triangle intersection was studied. The surface of the targets was subdivided by triangles twice, obtaining low density of triangles used for intersection tests and high density of triangles used for ray tracing as the original ray tubes. After ray-tracing program, the electromagnetic scattering problem could be solved by physical optics (PO) integration. The results of the proposed method were compared with those in the references. The good agreement between the results proved the preciseness of this method. And the efficiency of the method was proved by the results of different densities of subdivisions.