The Zn(Ⅱ) phthalocyanine sensitized TiO_2 (ZnPc-TiO_2) nanoparticles were prepared by hydrothermal method via impregnation with ZnPc. The as-prepared photocatalysts were characterized by X-ray diffractometry (XRD) and diffuse reflectance spectroscopy (DRS), and the surface photovoltage spectroscopy (SPS) and photocatalytic degradation of rhodamine B (RhB) were studied under illuminating. The experimental results indicate thatTiO_2 sensitized by ZnPc extends its absorption band into the visible region effectively, and the sensitized TiO_2 has higher activity than TiO_2 (Degussa P-25) under the simulated solar light and the visible light. Based on the DRS and SPS results, the mechanism about the photogenerated carrier transfer between TiO_2 and ZnPc is proposed. At a lower ZnPc content (≦0.20 μmol/g), ZnPc monomer acts as the electron donor, which provides the photoinduced electrons to the conduction band of TiO_2. These photoinduced electrons can transfer to molecular oxygen (O_2), leading to the formation of active species, such as superoxide/hydroxide radicals and singlet oxygen, which is beneficial to the photocatalytic reaction. While at a higher ZnPc content (>0.20 μmol/g), the formation of ZnPc dimer results in the decrease of photocatalytic activities of ZnPc-TiO_2 photocatalyst.