The aim of this study was to investigate the phase transformation and kinetics of the solid-state reaction of CaO?V2O5, which is the predominant binary mixture involved in the vanadium recovery process. Thermal analysis, X-ray diffraction spectroscopy, scanning electron microscopy, and energy dispersive spectrometry were used to characterize the solid-state reaction of the samples. The extent of the solid reac-tion was derived using the preliminary quantitative phase analysis of the X-ray patterns. The results indicate that the solid reaction of the CaO?V2O5 mixture is strongly influenced by the reaction temperature and CaO/V2O5 mole ratio. The transformation of calcium vanadate in-volves a step-by-step reaction of CaO?V2O5, CaO?CaV2O6, and CaO?Ca2V2O7 depending on the CaO/V2O5 mole ratio. The kinetic data of the solid reaction of the CaO?V2O5 (1:1) mixture followed a second-order reaction model. The activation energy (Ea) and preexponential factor (A) were determined to be 145.38 kJ/mol, and 3.67 × 108 min?1, respectively.