In order to study the effect of laser speckle on target detection, the theoretical analysis of the statistical characteristics of the scattering field when the plane wave laser irradiates the rough sphere and cone target was carried out by using the physical optics approximation method, and the second order statistical moment of the scattering field quantity of rough targets was derived. The variation of incoherent scattering component ratio of rough sphere and cone with roughness, scattering angle, radius, and target material is calculated numerically. The results show that the change of scattering angle has an effect on the incoherent component ratio of rough sphere scattering. The larger the roughness, the larger the proportion of incoherent component of target to the total scattering component. As the radius of the rough sphere becomes smaller, the surface of the sphere becomes rougher. The peak position of incoherent component ratio of cone target scattering varies with roughness, but its peaks are all located in the direction of specular reflection. The incoherent component ratio of metallic materials is smaller than that of non-metallic polished aluminum materials, and the radius change is proportional to the incoherent component ratio. The research results provide some reference value for the study of laser scattering characteristics of more complex targets and laser speckle detection and identification.