Abstract: According to the development of missile technology, a scheme of IR/laser dual-mode common aperture optical system which could obtain the dual-mode information of objects was proposed. The basic parameters of the optical system were analyzed, the design method of the dual-mode common aperture system was researched, and the optical system was designed. The system achieved common-aperture imaging at long wave infrared and laser wavebands. The relative aperture of the IR subsystem is 1.26, and the modulation transfer function approaches the diffraction limit. The relative aperture of the laser subsystem is 0.63, which approaches the theoretical value. The energy distribution of the imaging spot is uniform, and the spot size hardly changes in the range of linearity.