Visible scattering characteristics of a space satellite are studied based on geometrical optics and radiation theory. The background radiation of the space satellite consists of direct solar radiation and scattered radiation of the earth and atmosphere. Geometrical and illumination models of the space satellite are established according to target structure and background characteristics. Target surface appearance is analyzed and the ray incident to target surface follows a Nth cosine scattering distribution approximately. A mathematical model of target scattering characteristics is established in terms of energy conservation law and Nth cosine scattering distribution properties of surface material. The relative position of the sun, the earth and the observation satellite in target body coordinate system is determined by vector coordinate conversion. Energy distribution and magnitude characteristics on the entrance pupil of the detector are simulated by its given physical dimension and surface physical parameters. The maximum magnitude of irradiance from target body and solar sail on the entrance pupil of the detector is 10-12 W/m2. Simulation results indicate the solar sail cannot be neglected when the target characteristics are analyzed and it can provide reference data to visible detection of space targets.