[en] The plane-wave function method, based on density functional theory, has been used to calculate the adsorption, electronic band structures and optical absorption spectra of molecular and dissociative catechol adsorbed on TiO₂ anatase (1 0 1) surface. The obtained electronic structures of anatase (1 0 1) surface are similar with the previous theoretical works for anatase bulk. Our calculations reveal that one type of molecular catechol adsorption on (1 0 1) surface almost has no effect on the anatase optical absorption threshold; while another type of molecular adsorption and several dissociative adsorptions on (1 0 1) surface could lead to large red shifts of the absorption threshold. The dissociative adsorption at the defect site of (1 0 1) surface is also examined, and causes the strongest light absorption in the visible region. These results are in agreement with other experimental and theoretical studies reasonably. It is very important for the understanding and further development of photovoltaic materials that are active under visible light