The removal efficiency of microcystin-LR in water and the influencing factors by combined process of solar irradiation and S-doped TiO2 were studied in detail, in which S-doped TiO2 photo-catalyst with high sunlight activity was prepared by acid catalyzed hydrolysis method using thiourea as sulfur source. The experiment results showed that MC-LR could be more effectively oxidized by the solar/S-doped TiO2 process than by solar/ TiO2 process, whose removal effect were about 70% and 55% after 40 min’s irradiation, respectively. Pseudo-first-order model could be used to simulate the oxidation process. Degradation rate could be greatly affected by the concentration of H2O2, the optimum concentration for the system of solar/S-doped TiO2 was found to be 20mg/L, which was 5mg/L higher than that of solar/TiO2 system. Humic acids decreased the degradation rate, and solar/S-doped TiO2 process more easily affected, for the humic acids could not only compete with molecular MC-LR for radicals but also adsorb part of sunlight which can excite radical with TiO2.