In2O3 nanofibers (NFs) and toruloid nanotubes (TNTs) were fabricated by conventional electrospinning process and their sensing properties toward H2S gas were researched. Thermogravimetric analysis, x-ray diffractometry, energy dispersive spectroscopy and scanning electron microscopy were carefully used to investigate the structures, chemical compositions and morphologies of these samples. The novel structure (TNTs) first used nonpolar mineral oil as the control agent of morphology, and the principle of forming toruloid nanotubes was studied. Phase separation plays a critical role in the process of forming toruloid nanotubes structure automatically. The new application of phase separation provided a simple and effective approach for controlling structure. The research indicated that thin-walled toruloid nanotubes showed higher responses toward H2S compared to nanofibers or thick-walled toruloid nanotubes. Additionally, their excellent selectivity can be attributed to the special gas-sensing mechanism of In2O3 for H2S.