According to the environment during launch and on orbit, special design was carried out to improve spatial environment adaptability for ratioing radiometer which consists of integrating sphere, diffuser shutter and electronic optic cut. Weak part of ratioing radiometer was strengthened after making mechanical simulation. The temperature stability under thermal vacuum environment was realized by limiting the power of components and surface heat treatment. The radiation-proof ability was guaranteed by employing space-grade optical coating and making structure shield. Spatial environment adaptability was verified by mechanical, thermal vacuum and space radiation experiments. Mechanical testing results show that the fundamental frequency of the ratioing radiometer is about 540 Hz. The variation of the ratio for sun view to diffuser view of ratioing radiometer after mechanical experiments is within 0.31%. The structural strength and rigidity of the ratioing radiometer could meet the design requirement that the fundamental frequency should be above 100 Hz. The electronic components of the ratioing radiometer maintain normal during thermal vacuum experiments. The degradation of directional/hemisphere reflectance for the ratioing radiometer at 485 nm after space radiation tests is within 2%, while the change of directional/hemisphere reflectance in longer wavelength is negligible. The above results show that the ratioing radiometer has good space adaptability and is able to work steadily and reliably in complex space environment, which meets the needs for aerospace application requirements.