In consideration of the effect of stray light on the measurement accuracy of a space-borne differential optical absorption spectrometer for monitoring atmospheric trace gases, several stray light removing mechanisms including a light shield and other baffles were developed to suppress the stray light, and the properties of the stray light were analyzed. With TracePro model, the stray light removing of UV channel 1(240-315 nm) in the system was evaluated ,then the first and second order scattering paths were determined by simulation analysis. On the basis of stray light paths, the stray light removing for revised system was analyzed, and Point Source Transmittance(PST) was calculated. The obtained PST value shows that the light shield and other mechanisms have suppressed the stray light effectively, PST values are less than 3×10-5, and stray radiation ratio in a central field is 5.472×10-4. Furthermore, the final stray light suppressing level of the system satisfies the requirement of design index. Moreover, the edge filter method is used to measure the stray light level, and the results indicate that the stray light in the central field is 8.167×10-4, which is close to the simulation results and proves the simulation result to be credible.