Abstract: Because micro-light remote sensing can detect ground objects under low illumination conditions such as nighttime and twilight, this remote sensing camera uses micro-light remote sensing to complement the traditional visible light remote sensing to achieve observation in visible light all-day long. Considering the system's long focal length(500 mm), large field of view(5°×2°),large relative aperture(F number 3.8),miniaturization and high optical efficiency, this remote sensing camera used off-axis three-mirror system structure and common light path for double detectors, subfield of view to achieve simultaneous imaging from micro-light and visible light detectors. The optical system design and imaging quality of the optical system of the camera were analyzed in detail. The results show that the modulation transform function (MTF) of traditional visible light fields of view are more than 0.4 at the Nyquist frequency of 200 lp/mm and the MTF of micro-light fields of view are more than 0.75 at the Nyquist frequency of 77 lp/mm and the MTF is close to the diffraction limits. Based on development and launch processes of optical load, system tolerances were analyzed from the four processed of machining, alignment, primary focusing and non-focusing, and the result of tolerant assignment was given. In addition, the extensibility of the optical system was illustrated.