The effects of illumination manners on the photocatalytic degradation of organic contaminants were studied with the TiO2/ITO photoanode. The degradation process and the hole scavenging ability were analyzed by light intensity test. The results showed that the photocatalytic degradation rates of phenol, humic acid and acid orange under backside illumination increased by 16.19%, 26.09% and 38.87%, respectively, compared with those under positive illumination. That was because the illumination intensity of positive illumination lost when the light passing through the solution, thus the illumination intensity on the surface of the photoanode reduced. The increased degradation rate of organic pollutants under backside illumination was positively correlated with the light adsorption ability of organic pollutants. The backside illumination improved the hole trapping ability by avoiding the illumination loss, resulting in a larger photocurrent compared with the condition without contaminants.