An experimental installation using a proto of optical antenna telescope with diameter 150 mm, field of view ±0.17 ° and receive wavelength 974 nm has been built to measure the forward scattering, and the result shows that there are two energy peaks of original-road-returned stray light at 0.35° and 1°. By analysis of these two stray light peaks, a measure to eliminate forward scattered stray light of telescopic system is put forward. By analysis of the influence of primary and secondary lens focal power distribution on stray light of optical antenna, concluded that reduce the focal length of primary mirror can reduce the original-road-returned stray light.