Abstract: In order to meet the needs of data acquisition, feature extraction of radar echo characteristics of combinatorial target placed on the rough surface, Topp model and dielectric complex permittivity calculation formula are used to simulate the real and imaginary parts of the soil dielectric parameter, the soil surface is simulated with the Weierstrass-Mandelbrot fractal function, the electromagnetic scattering from the composite model consisting of soil surface and combinatorial target placed on it is studied by the finite-difference time-domain method, and the angle distribution curve of composite scattering coefficient is simulated. The simulation results show that the composite scattering coefficient oscillates with the scattering angle, and the scattering enhancement effect occurs in the mirror reflection direction; the larger the root mean square of the fluctuation of soil surface, the larger the composite scattering coefficient; the larger the fractal dimension, the larger the composite scattering coefficient; although the influence of the soil moisture content on the composite scattering coefficient is small, there are fixed rules to follow; there is no fixed rule for the influence of the scale and dielectric constant of combinatorial target, incident angle on the composite scattering coefficient; scale interval and spatial fundamental frequency have no effect on the composite scattering coefficient.