In order to study the Radar Scattering Characteristics of Low Altitude Aircraft over the Sea, a new method called AIPO+MEC is proposed is this paper. The interaction between object and ocean surface is computed by using the Iteration Physic Optic (AIPO) method, and the Method of Equivalent Currents (MEC) is used to compute the edge diffraction. By comparing the bistatic scattering coefficient of metal cube located on ocean surface which is computed by the method already exists, the validity of this method is proved. The realistic ocean surface is simulated by rough surface with PM(Pierson-Moskowitz)spectrum. The back scattering coefficients of three typical stealth aircraft over ocean surface, which are compared with that of aircraft in free space and that of aircraft over the plane, is calculated by using AIPO+MEC. The result shows that, the back coefficients increase due to the interaction between the aircraft and ocean surface, and the angle distribution of scattering coefficients of aircraft over ocean surface are gentler than that of aircraft over plane. The conclusion of this paper has a certain theoretical guiding significance for detection of low altitude target over the sea surface in modern war.