Herein, we employ a combination of electrospinning and hydrothermal approaches to synthesize 1D SnO2-In2O3 nano-heterostructures with a series of morphological evolutions. Through variations in the mole ratio of Sn4+ and In3+ ions in hydrothermal condition, several 1D SnO2-In2O3 heterogeneous morphologies have been realized. The proposed growth mechanism for 1D nano-heterostructures is expected to be a nucleation-growth process. In2O3 nanofibers, as templates, provide numerous nucleation sites for the growth of SnO2 nanostructures. As the Sn4+ concentration increases, the SnO2 nucleus can start to grow from the surface of In2O3 template and extend out along the lateral direction until adjacent grains begin to be connected, forming morphological evolutions. The sensor of SnO2 nanocylinders, grown on In2O3 nanofibers (SI-3 sample), exhibits highest response value at optimal operating temperature. The sensor based on SI-3 sample displays quicker recovery capability towards ethanol gas. A rapid recovery rate can be ascribed to the spillover effect and high surface area. The gas-sensing mechanism of 1D SnO2-In2O3 nano-heterostructures has been discussed.