V 3O 7⋅H 2O nanobelts were prepared by a hydrothermal method at 190 ∘C using V 2O 5⋅ nH 2O gel and H 2C 2O 4⋅2H 2O as starting agents. The nanobelts obtained have diameters ranging from 40 to 70 nm with lengths of up to several micrometers. Their morphology and structure have been characterized by XRD, SEM, TEM and IR spectroscopy. The effect of the annealing temperature on the morphology of the resulting product has been investigated. XRD and SEM showed that thermal annealing of the V 3O 7⋅H 2O sample in air led to the collapse of the V 3O 7⋅H 2O nanobelt structure and the convert into V 2O 5 nanobelts. For the first time V 2O 5 nanobelts with an ultrahigh aspect-ratio have been obtained in air. Furthermore, electrical conductivity and static magnetic susceptibility measurements have been carried out.