A visible/infrared integrated space remote-sensing imaging scheme is proposed in this study to satisfy the all-weather and all-day remote-sensing application requirements in the fields of battlefield situation awareness, environmental pollution monitoring, and emergency disaster reduction. The proposed system covers visible panchromatic/multispectral, middle-wave and long-wave infrared spectral bands. The spatial resolution of the aforementioned spectral bands can reach 2 m/8 m, 8 m, and 16 m, respectively, and the imaging width exceeds 15 km. The technical parameters of the optical system are analyzed and determined, and the design scheme of the visible/infrared common-aperture modular optical system is proposed. The design and analysis of each module of the optical system and the entire optical system are realized. The design results show that the imaging quality of each module of the optical system and the entire optical system is close to the diffraction limit. Each module can be assembled and tested separately, facilitating the modularization development of the visible light/infrared complex optical system. The complexity and time taken for development of the multispectral, multifocal, integrated optical system can be effectively reduced. Therefore, the visible/infrared common-aperture modular optical system has a significant engineering application value.