Metal-ion-doped TiO2 nanoparticles were prepared with sol-gel method. The photocurrents of these metal-ion-doped TiO2 electrodes were measured at different electrode potentials and different excitation wavelengths, and different photoelectrochemical behaviors were observed. The phenomenon of pn conversion was observed for Fe3-- doped TiO2 electrode. however, the characteristic of pure n-type semiconductor was observed for lanthanide ion (such as La3+, Nd3+, Pr3+, Sm3+ and Eu3+), Zn2+, Cd2+, Cr3+ and Co2+-doped TiO2 electrodes. The effect of the content of Zn2+ on photocurrent was investigated and the result showed that the incident photon conversion efficiency (IPCE) was the largest when the content of Zn2+ was 0.5%.