SnO2 nanoparticles with controlled crystallinity, morphology and gas sensitivity have been synthesized by four modified wet chemical processes using the same granular Sn but different solvents and preparation routes. The thermal decomposition, crystalline phase, morphology and gas sensitivity of precursors and well-crystallized SnO2 nanoparticles were characterized by means of differential thermal analysis, X-ray diffraction, scanning electron microscopy, field emission transmission electron microscopy, energy dispersive X-ray spectroscopy and gas sensitivity measurement system. Results indicated that SnO2 precursors showed quite different endothermic heat behavior, crystallinity and particle size, which were strongly depended on preparation processes. SnO2 nanoparticles from different precursors showed the same typical tetragonal rutile SnO2 structure but different particle size and morphology. The gas sensitivity of SnO2 nanoparticles was investigated, which was strongly correlated with SnO2 nanoparticles. At last, the formation mechanism including nucleation and growth of SnO2 nanoparticles was proposed based on wet chemical reaction equations. (C) 2013 Elsevier B.V. All rights reserved.