Based on the density functional theory calculation using B3LYP hybrid method, a distorted square pyramidal (V4+=O)(O-f)(4) unit in a reduced and dehydrated VAPO-5 is formed by the vanadium (IV) oxide ion anchored to two neighboring 12-membered TO4 rings of the aluminophosphate-5 lattice. By breaking two V-O-T bonds on one twelve-membered-ring to form another V=O bond, V4+ can be oxidized to a tetrahedral di-oxo V5+O4 unit. The computed structures of vanadium oxide species have been confirmed by Raman spectroscopy.