The present study investigates the formation mechanism of hollow SnO2 nanofibers and the form of nanograin growth in nanofibers. SnO2 hollow nanofibers were fabricated by directly annealing electrospun polyvinylpyrrolidone (PVP)/Sn precursor composite nanofibers. In this approach, an appropriate proportion of PVP/Sn precursor with co-solvents established a system to form core/shell PVP/Sn precursor structure, and then PVP was decomposed quickly which acted as sacrificial template to keep fibrous structure and there existed a Sn precursor/SnO2 concentration gradient to form hollow SnO2 nanofibers due to the Kirkendall effect and surface diffusion during the calcination process. This deduction was also confirmed by experimental observations using transmission electron microscopy. The study suggested that surface diffusion and lattice diffusion were both driving force for nanograin growth on the surface of SnO2 nanofibers. As supporting evidence, the tetragonal rutile SnO2 hollow nanofibers were also characterized by X-ray diffraction, scanning electron microscopy and Brunauer–Emmett–Teller analysis.