The preparation of high-quality indium antimonide (InSb) single crystal is the key to the development of large-format infrared focal plane devices and new substrate materials for high-temperature infrared detectors. However, in the process of growing InSb by the Czochralski method, the appearance of surface impurities will seriously affect the yield. The X-ray photoelectron spectroscopy (XPS) technology is used to study the composition of the impurity layer on the surface of InSb crystals in production, the main sources and their effects are analyzed, and corresponding process measures are adopted to improve them. The results show that the main components of the impurity layer on the surface of InSb crystals are a mixture of In₂O₃, Sb₂O₃ and Sb₂O₅ as well as carbon contamination, the thickness of which is not more than 40 nm. By optimizing the processing of the single crystal furnace treatment and the protective atmosphere, the surface impurities are greatly reduced, laying the foundation for obtaining high-quality crystals.