Here,carbon dots (CDs) only or nanocomposites of CDs and TiO2 (CDs-TiO2) were used to decorate titanium dioxide nanotube arrays (TiO2NTs) in situ by solvothermal method.Two initial states of TiO2NTs were prepared for contrast,including the amorphous TiO2NTs (TiO2NTs-0) just experienced anodic oxidation process and that further calcined TiO2NTs (TiO2NTs-450).It was found that the newborn CDs or CDs-TiO2 were more likely to anchor on TiO2NTs-0 than the calcined TiO2NTs-450,and more Ti-C bonds were found in the composites which were derived from TiO2NTs-0 after the solvothermal treatment.An evident photocurrent could be demonstrated for either CDs or CDs-TiO2 decorated TiO2NTs once exposed to visible light.And CDs-TiO2NTs-0 showed the highest photocurrent density (4.51 μA·cm-2).However,the results of photodegradation measurements revealed that CDs-TiO2 decorated TiO2NTs with different initial states (especially CDs-TiO2-TiO2NTs-0) showed more excellent photocatalytic activity under both ultraviolet (UV) and visible light illumination.