The tungsten-doped TiO2 powders were prepared by calcination process at different temperatures, with TiO2 as starting materials and WO3 as additive. The XRD and SEM were used to investigate the influence of calcination temperatures and the content of WO3 on the phase transformation of TiO2 powders. Moreover the transformation mechanism was discussed. The results show that the phase transformation from anatase to rutile of TiO2 powders is mainly attributed to the additive WO3. WO3 can promote the phase transformation and lower the transformation temperatures. The phase transformation of TiO2 are caused by two aspects of WO3, one is the replacement of some Ti4+ by Wn+ in TiO2 crystal lattice, and the other is the redox reaction between WO3 and TiO2. The replacement of Ti4+ by Wn+ during the redox reaction is believed to be the major factor influencing the phase transformation.