In order to meet the needs of radar target detection, recognition and classification above the soil surface, the spatial domain synthesis method is chosen to generate the soil surface with altitude fluctuation that obeys the Alpha-stable distribution. The Topp model is chosen to simulate the dielectric constant of the soil, and the method of moments is applied to study the composite electromagnetic scattering of the soil and the triangular cross-section column moving target above it under the conical wave incident condition, and the variation curve of composite scattering coefficient with scattering angle is obtained. The effects of lateral translation, longitudinal translation, rotation and incident angle of electromagnetic wave on composite scattering coefficient are discussed.