In order to evaluate the ability of a space-based optical system to suppress off-axis stray light, a large-field, multispectrum space-based stray light test method based on point source transmittance (PST) is proposed in this paper. A stray light test facility is constructed using multiple laser sources, large aperture off-axis reflective parallel light tubes and a high-precision positioning mechanism to evaluate the PST index of stray light in the visible and near infrared bands for a space-based optical system. Based on theoretical analysis, experimental measurements of standard lenses in various wavelength bands have proven that the dynamic range of the facility in the visible light band is 10-6 and in the infrared band is 10-3. The facility has the advantages of wide range of detectable wavelengths, high automation, and large dynamic range. The test results can be used for correction of the hood, which provides a reliable traceability basis for the stray light suppression of a space-based optical system. © 2021 SPIE