Nb or Ta doped vanadium dioxide (VO2) thin films were grown on r-plane sapphire substrates by a metal-organic decomposition (MOD) method. Their crystallinities of the VO2 thin films were evaluated by XRD, AFM and XPS. It was clarified that polycrystalline fine particles having a moth-eye structure were grown and Nb or Ta ions were gradually replaced by V sites in all the samples. Moreover, it was found that the phase transition temperature measured by a spectrometer indicated 61-39°C for Nb doped samples and 57-47°C for Ta doped samples by doping from 1 to 3 mol%. The change in transmittance before and after the phase transition temperature tended to widen the transition temperature range as the doping concentration increases due to the gradual phase transition change. It was considered that the dopant of Nb or Ta ions added to replace V sites had an effective role on changing the phase transition phenomenon of VO2. Furthermore, FDTD simulation for nanoscale porous moth-eye structure VO2 thin films was carried out to compare with the data measured by a spectrometer, and it was in good agreement.