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　(101)　surface.　The　obtained　electronic　structures　of　anatase　(101)　surface　are　similar　with　the　previous　theoretical　works　for　anatase　bulk.　Our　calculations　reveal　that　one　type　of　molecular　catechol　adsorption　on　(101)　surface　almost　has　no　effect　on　the　anatase　optical　absorption　threshold;　while　another　type　of　molecular　adsorption　and　several　dissociative　adsorptions　on　(101)　surface　could　lead　to　large　red　shifts　of　the　absorption　threshold.　The　dissociative　adsorption　at　the　defect　site　of　(101)　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.　(c)　2006　Elsevier　B.V.　All　rights　reserved.