In order to improve the prediction accuracy of radar scattering characteristics of helicopters, the computational electromagnetics (CEM) method is established to analyze radar scattering characteristics, and the influence of coating on radar cross section (RCS) characteristics is studied. First of all, geometric model and mesh generation for complex target (such as helicopter) are conducted and the electromagnetic field information on the space grid unit is obtained for the simulation and analysis of the electromagnetic field. Secondly, the finite difference time domain (FDTD) method combined with conformal technique is effective in the treatment of dielectric objects and equivalent impedance method for dielectric coated objects through the calculations on the dielectric ball and the conductor ball coated with electromagnetic medium. The results show that the calculation results of the FDTD method agree well with the series solution. Then, the RCS characteristics of the metal rotor and the coated rotor are calculated and compared, and the influence of RCS on the characteristics of the fuselage before and after the coating is analyzed at different angles of incidence. It is demonstrated that the RCS reduction effect is obvious through the rotor surface coated with radar absorbing material (RAM). The whole body coating in the strong scattering parts can significantly reduce RCS and the use of coating plays a key role in the design of stealth helicopter.