In electromagnetic (EM) simulation, conventional triangular patches are implemented to discrete the surface of the conducting objects. Based on the Rao-Wilton-Glisson (RWG) basis function and the continuity of the surface current across the boundary with different mesh sizes, the EM scattering of the conducting objects are presented. The radar cross section (RCS) are acquired for conducting objects by the physical optics (PO). The numerical results can be compared with those from the commercial software (Feko), which indicates the accuracy and effectiveness of the method in this letter.