SnO2 nanofibers were fabricated by electrospinning, using SnCl(2 center dot)2H(2)O as the raw material. The influences of ZnO doping on the morphologies, structures, and compositions of the SnO2 nanofibers were studied by introducing different amounts of ZnO into the SnO2. The crystallography and microstructures of the synthesized SnO2/ZnO composite nanofibers with different molar ratios of Sn to Zn were investigated using thermogravimetric/differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. The obtained SnO2/ZnO composite nanofibers with different ZnO contents had hollow hierarchical structures composed of nanocrystals. Different amounts of ZnO gave different structures. The characterization results showed that the introduction of ZnO into SnO2 played an important role in the SnO2 nanofiber structure. The gas sensing properties of sensors based on different ZnO-doped SnO2 nanofibers were tested. The results indicated that the methanol-sensing performance of the sensor containing SnO2/ZnO in a molar ratio of 1:1 was better than those of the others. The sensing mechanisms of ZnO-doped SnO2 nanofibers were examined in detail. Possible reasons for the enhanced response of the SnO2/ZnO-based sensor with a molar ratio of 1:1 are substitutional doping of Zn into SnO2, the catalytic effect of ZnO addition, and the inhibitory effect of excess ZnO, as well as the heterojunction across the SnO2 and ZnO interface.