Thermochromic VO2 thin films are fabricated by atomic layer deposition with vanadyl acetylacetonate as the precursor. The crystallization process has been performed by post-annealing process, i.e. rapid thermal annealing. The effect of annealing temperature on thermochromic properties is investigated. Though the transmittance increases with increasing annealing temperature, a moderate temperature is suggested by the consideration of atomic inter-diffusion between TiO2 and VO2 layers. It is found that an oxygen-deficient phase of V2O3 appears at low annealing temperatures, while an oxygen-ambient phase of V2O5 presents at high temperatures. Additionally, a ternary compound, Ti3V6O17 is dominant beyond 700°C. The crystalline behavior of monoclinic phase of VO2 and Ti3V6O17 observed from the X-ray diffraction pattern is further examined by high resolution transmission electron microscope. The depth profiling in binding energies of V 2p, O 1s and Ti 2p orbits are compared.