Plasma-nitridation was taken place to dip-coated Cu-doped TiO2 film. XPS analysis reveals that the ionic states of Ti and Cu in the Cu-doped TiO2 films are Ti4+ and Cu+, respectively. After nitrogen plasma treatment, oxygen atoms are released by substitution of nitrogen atoms in the TiO2 matrix, so that Cu+ is oxidized to generate Cu2+ and at the same time oxygen vacancy is formed. The absorption edge of both Cu-doped and plasma-nitrided Cu-doped TiO2 did red shift. Visible-light responsive photocatalytic activity of the Cu-doped TiO2 film degraded after nitrogen plasma treatment.