SnO2/In2O3 composite hetero-nanofibers were synthesized based on a modified bipolar electrospinning with double jets. SnO2/In2O3 composite hetero-nanofibers were further modified by oxygen plasma in a radio frequency (RF) plasma treatment chamber at low temperature. The morphology and structure of treated SnO2/In2O3 composite hetero-nanofibers were characterized by using XRD, SEM and TEM. The composition and specific surface of treated SnO2/In2O3 composite hetero-nanofibers were characterized by EDX, XPS and BET. Both SnO2 and In2O3 nanofibers in the treated SnO2/In2O3 composite heteronanofibers are hierarchical and hollow structure as same as the ones before treated. The morphology of treated SnO2 and In2O3 nanofibers changed significantly. The porosity and specific surface area of the treated composite nanofibers were bigger than the ones of untreated sample. The gas sensing properties of the treated SnO2/In2O3 composite hetero-nanofibers to formaldehyde were tested. The treated composite nanofibers exhibit high response values and low operating temperature. Cross-responses and humidity effect of the treated composite nanofibers sensor were tested. The gas sensing mechanism of the SnO2/In2O3 composite hetero-nanofibers treated by oxygen plasma was analyzed. (C) 2014 Elsevier B.V. All rights reserved.