Abstract: Homo heterojunction or hetero heterojunction will form at the surface of two kinds of different semiconductor due to the difference of electronic affinity and band gap width. The interface carrier mobility can be improved by means of Fermi level effect at interface of heterojunction, which improves the gas sensitivity perfor-mance of gas sensor. The coaxial heterocomposite In₂O₃/SnO₂ nanofibers were fabricated by a self-designed multilayer coaxial electrospinning device. The bigger In₂O₃ nanoparticles on the outer layer of In₂O₃/SnO₂ fibers grow on the surface of the SnO₂ nanoparticles on the inner layer of In₂O₃/SnO₂ fiber, which forms the hollow hierarchical fiber structure. N-N homo-heterojunctions interface between of In₂O₃ and SnO₂ nanoparticles will enhance electron mobility, surface activity and the content of adsorption oxygen, which will improve the adsorption capacity of In₂O₃/SnO₂ sensor to formaldehyde. The response of coaxial hetero-nanofiber In₂O₃/SnO₂ sensor is 14.12×10^-6 to 50 ×10^-6 formaldehyde, are 3.22 times, 3.84 times and 1.51 times of that of SnO₂, In₂O₃ and mixed hetero-nanofiber In₂O₃/SnO₂ sensor at 250℃. The coaxial hetero-nanofiber In₂O₃/SnO₂ sensor also shows excellent cross-selectivity to formaldehyde, ethanol, acetone, ammonia, toluene and methanol. The coaxial hetero composite synthesized by coaxial electrospinning has application potential and development prospect to improve semiconductor function device.