Abstract: In order to improve the signal-to-noise ratio (SNR) of a vacuum environment particle detection device based on light scattering, this paper proposes corresponding optimization methods from the perspective of stray light analysis. Using TracePro optical simulation software, the effects of the surface absorptivity of mechanical structural components, the terminal light-absorbing structure, the transmittance of the window plate, and the position of the detector on the system’s stray light intensity were systematically analyzed, thereby providing optimization design methods for vacuum environment particle detection devices. Taking the stray light flux on the detector as the evaluation metric, simulation results show that increasing the surface absorptivity of mechanical structural components from 80% to 98% can reduce the stray light flux on the detector by 2 to 3 orders of magnitude. For the terminal light-absorbing structure, the light absorption capability of conical and bent tubes is about 20 times that of straight tubes. At the same time, increasing the transmittance of the window plate can also reduce stray light intensity to a certain extent. In addition, the system's SNR exhibits a monotonically increasing trend within a detection distance range of 100 to 250 mm. Considering the compactness of the device structure, the detection distance is controlled within 250 mm.