SnO2/In2O3 hetero-nanofibers composite was synthesized by using a modified electrospinning system with double jets of positive and negative polarity electric fields. The SnO2/In2O3 hetero-nanofibers with a netted structure composed of SnO2 and In2O3 nanofibers were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). Both SnO2 and In2O3 nanofibers were hierarchical structures with many nanocrystallites. The SnO2 and In2O3 showed very different nanocrystallites sizes in the SnO2/In2O3 hetero-nanofibers composite. A gas sensor was fabricated based on SnO2/In2O3 hetero-nanofibers composite. The operating temperature of the gas sensor was 375 C. The response value of the gas sensor based on SnO2/In2O3 hetero-nanofibers was higher than the ones of SnO2 nanofibers and In2O3 nanofibers sensors, respectively, in formaldehyde concentration range of 0.5-50 ppm. Cross-responses of SnO2/In2O3 hetero-nanofibers sensor to formaldehyde, ethanol, ammonia, acetone, toluene and methanol were tested. The response value of the SnO2/In2O3 hetero-nanofibers sensor decreased when the relative humidity increased. The sensing mechanism of the SnO2/In2O3 hetero-nanofibers gas sensor was briefly analyzed. (C) 2012 Elsevier B.V. All rights reserved.