Abstract: In order to improve the miniaturization and integrated level of the optical system of television and laser finder/illuminator carried on small unmanned aerial vehicle, a television and laser transmitting/receiving common-aperture optical system was designed. By combining the methods of spectral beam split and polarizing beam split, the common aperture of television, laser transmitting and laser receiving was achieved. Using optical passive athermal design method, the athermalization design was realized in the temperature range from −40 ℃ to 65 ℃. The designing scheme of common-aperture optical system and the athermal design method were introduced, the design and optimization process of this optical system was expounded, and then the imaging quality of this optical system and the changes of optical properties under high and low temperature conditions were analyzed by optical design software. Analyzing results show that the optical properties of the television and laser transmitting/receiving common-aperture optical system can satisfy the requirements of design specifications, and the performances of this optical system will not degrade significantly in the temperature range from −40 ℃ to 65 ℃.