In order to increase the prediction accuracy on helicopter radar scattering char acteristics, the computational electromagnetics method (CEM) is established to a nalyze radar scattering characteristics, and the influence of stru cture parameters on radar cross section (RCS) characteristics is studied. The d iff erential forms of Maxwell′s equations are taken as the governing equations for s olving electromagnetic property, computational electromagnetic grids are generat ed by adopting the Yee grid technology, and the governing equations are solved by temporal and spatial discretization with central difference scheme. The perfect matching layer (PML) technique is employed as th e absorbing boundary conditions, and the numerical method with high precision fo r helicopter RCS is established by combined with the equivalence principle of ne arfar field extrapolation. Twodimensional conductor cylinder with infinite l ength and threedimensional metal cube are taken as numerical examples respecti vely. The results show that CEM has higher precision than the high frequency met hod obviously. On this basis, researches on the influence mechanism and variatio n characters of airfoil thickness, airfoil camber and the number of blades on ro tor radar scattering characteristics are carried out, and RCS characteristics of fuselage with different structure parameters are computed, then the influence m echanism of short wings and horizontal tails on fuselage strong scattering chara cteristics is analyzed. It is demonstrated that blade tip is one of the signi ficant scattering sources of rotor, rotor with thin airfoil can improve the rada r scattering performance effectively, and short wings and horizontal tails can i ncrease the RCS of fuselage in different angles, which should be taken into key consideration in stealth design of helicopter. 