Abstract: The degradation of optical system in space environment has an important effect on the measuring precision of satellite-borne remote sensing instruments. The solar diffuser is an important tool of radiation intensity scaling for satellite-borne optical remote sensing instrument. In this paper a comparison of the decay of solar diffusers in ADEOS/TOMS and Earth Probe/TOMS, and analyses the effects of atomic oxygen and solar UV radiation on solar diffuser is given. The results show that the decay coefficients of solar diffuser in the wavelength of 360 nm due to solar UV radiation exposures and atomic oxygen erodes are 0.00049/h and 1.2 × 10^-17cm² respectively. So the effect of atomic oxygen erodes is about 5 times of solar UV radiation exposures in the altitude of 800km during the solar activity minimum. For the solar activity maximum, the effect of atomic oxygen will greatly increase. In the early days of satellite orbit, however, the effect of solar UV radiation exposures on solar diffuser may increaise about 4 times. It may be due to the contamination. But our analyses havn’t find the interaction between atomic oxygen erodes and contamination effect.