Titanium doped zinc oxide (TiZO) thin-film transistors (TFTs) were fabricated with the active layer deposited by the cosputtering of Ti and ZnO targets. We fabricated TiZO TFTs under various sputtering powers, effects of which on the performance of TiZO TFTs were investigated. The results suggest that the effective Ti doping concentration is significant for excellent electrical properties. The optimal electrical performance was obtained at 60 W of ZnO sputtering power and 80 W of Ti sputtering power. The changes in the crystalline structure, surface morphology and optical transmittance of TiZO thin films were examined according to the sputtering power, which agreed well with the variation of device performance.