The invention relates to the technical field of collimation control, and provides an optical system capable of improving adaptability of an aiming device to an offset target prism. The main aiming device is a photoelectric collimator, the mainly related optical system of the photoelectric collimator comprises a telescope system, a luminescent system, a beam splitter prism and a cross shaft, the telescope system and the luminescent system are perpendicular with each other and achieve follow-up together with the cross shaft, the luminescent system is internally provided with a beam shaping lens group and a reticle, and a light source passes through the beam shaping lens group, is focused on the reticle and then enters the target prism through the beam splitter prism and the telescope system. According to the optical system capable of improving the adaptability of the aiming device to the offset target prism, by means of optimization design on semiconductor laser light source shaping and a follow-up mechanism assembly, the requirements that on the condition that the target prism has up-and-down offset of +/-25 mm and left-and-right offset of +/- 30 mm relative to a luminescent system outgoing light spot, collimation zero offset is not larger than 10 inches, and the collimation measurement precision meets 15 inches are met.