Nano-structured Ti and Ga co-doped ZnO (TGZO) thin films were synthesized with 1.0%(atomic fraction, the same below) Ga and different concentrations of Ti by sol-gel spin coating method. The influences of Ti doping concentration on the phase composition, surface morphology, electrical and optical properties of TGZO films were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis spectrophotometer, four point probes and Hall measurement system, respectively. The results show that all TGZO thin films exhibit polycrystalline with a hexagonal wurtzite structure and slight (002) preferred orientation, which show excellent transmittance (>86%) in the wavelength range between 380 nm to 780 nm. With the increase of Ti content, both the grain size and the average transmittance of visible light of the TGZO film increase first and then decrease, while the optical band gap and resistivity decrease and then increase. The highest visible light transmittance is 92.82%, the narrowest optical band gap is 3.249 eV and the lowest resistivity is 2.544×10-3 Ω·cm obtained when doping 1.0% Ti.