Due to the excellent properties, multi-dimensional p-n heterojunction materials are widely used in the field of gas sensing. In this work, In2O3-modified Mn2O3 nanorod was prepared by a hydrothermal method. The composites had excellent detection performance for triethylamine (TEA). The composites had rich 0D-1D multi-dimensional nanostructures. The sensing properties of composites with different In/Mn ratios were investigated by adjusting the proportion of Mn. The test results showed composite material had high response, excellent selectivity, ultra-high resistance stability and repeatability during repeated testing. High specific surface area, abundant active sites by the formation of multi-dimensional heterojunction, and Mn3+/Mn4+ fast redox cycling of compound material made the excellent sensing performance. This work provided a reference for designing multi-dimensional heterostructures and high performance gas sensors.