Copper doped TiO2 nanoparticles were synthesized by hydrolysis of tetrabutyl titanate (Ti(OBu)4) and copper nitrate (Cu(NO3)2) in water-in-oil (W/O) microemulsions, consisting of water, Triton X-100, n-hexanol, cyclohexane and water. In this W/O system, Trinton X-100, n-hexanol and cyclohexane were used as surfactant, co-surfactant and organic solvent, respectively. The prepared nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The results show that the Cu-doped TiO2 nanoparticles synthesized by this method have a good dispersion character and relatively small sizes of about 80 nm. The XRD results show that the calcination temperature greatly influences the crystallization transformation. When calcined below 550 °C, the prepared sample is composed of anatase structure. When the calcination temperature increases to 650 °C, rutile phase appears besides the anatase phase. While doping amount has little effects on crystal phase. FTIR analysis indicates that most of the contained water and the residual organic surfactants can be removed by calcination.