This paper has systematically investigated the effects of 13 metal ion dopants on the photoreactivity and UV adsorption of TiO2 nanoparticle. The pure and ion-doped TiO2 nanoparticles were prepared using so-gel method. The absorption spectra of the TiO2 nanoparticles were obtained using UV-Visible spectrometer. The wavelength of the absorption edge of TiO2 was calculated using the tangent method. In general, different doping ion types were observed to exhibit different effects on the absorption spectra and photoreactivity of TiO2 nanoparticles. Ion concentrations were also shown to play a important role in the photoreactivity of the catalyst except Ag+, La3+, Zn2+ ions. Results reveal that red shift occurred to all ion-doped TiO2 nanoparticles with absorption edge ranging from 426 nm to 437 nm under optimal ion concentrations. Photocatalysis was shown to be inversely proportional to the amount of red shift of the absorption edge of implanted TiO2. Among the ions investigated, Ni-doped TiO2 nanoparticles have shown highest photoreactivity at the ion concentration 6.04×1017cm-3. The research results may provide references about enhancing the photoreactivity of TiO2 nanoparticles by applying metal ion doping.