In this paper, we introduce Lambert-Beer law into bidirectional reflectance distribution function in order to deduce a mathematical model for calculating the backscatter cross section of spherical cooperative target. And based on this theoretical basis, the experimental system that for measuring the backscatter cross section of spherical cooperative target is established. Using this test system, the relative intensity spectral data of echo signal of the spherical cooperative target with different materials was measured. At the same time, the spot images of spherical cooperative targets corresponding to the three typical emission power of 50 mW, 80 mW, and 300 mW are collected. According to the spectral data analysis, the backscattering cross sections of the cooperative targets with different materials are calculated. The results show that the laser radar cross section of the spherical cooperative target with refractive index of 1.46, 1.51, and 1.93 increases linearly with the increase of laser power. When the laser power is constant, the laser radar cross section of the spherical cooperative target with refractive index of 1.93 is significantly larger than that of the spherical cooperative target with refractive index of 1.46 and 1.51. This research provides a theoretical basis and data reference for the theoretical research and experimental measurement of the laser radar cross section.