Abstract: The unique barrier effect of the p-n junction can not only significantly change the optical and electrical properties of semiconductor composites，but also affect the sensitivity of gas sensors. In this paper，CuO/In₂O₃ composite nanomaterials with different mass ratios were prepared by the two-step hydrothermal method. The morphology and structure of the materials were analyzed by X-ray diffraction，scanning electron microscopy，transmission electron microscopy，and X-ray photoelectron spectroscopy. It was observed that CuO was a spherical hierarchical structure，and In₂O₃ nanoparticles were attached to its surface.Based on the gas sensing performance test，it was found that when the mass ratio of CuO and In₂O₃ in CuO/In₂O₃ composite nanomaterials was 1∶2，its sensitivity to n-butanol with a volume concentration of 100 × 10^-6 was 107 at 225 ℃ ，which was 57% higher than that of pure In₂O₃ nanoparticles. In addition，the sample also showed good selectivity and stability to n-butanol.

Key words: CuO/In₂O₃ nanocomposite；gas sensing properties；hydrothermal method；p-n junction