Cu-TiO2 nanocomposites with different Cu/TiO2 molar ratios were synthesized by a new simple chemical reduction method. The morphological structure and the surface species of Cu-TiO2 nanocomposites were determined by using UV-vis absorption spectroscopy, TEM, XPS, XRD, and EDX techniques. The photocatalytic cytotoxicity of Cu-TiO2 nanocomposites was investigated under UV-vis light irradiation. The cytotoxicity depends on the molar ratio of Cu to TiO2, ranging from 0.2 to 5.