A novel method for the removal of sulfur compounds in petroleum was put forward and investigated on the basis of the radiochemical reaction induced by gamma irradiation. Dibenzothiophene (DBT) dissolved in dodecane was employed as the simulated petroleum. The results showed that the removal efficiency of DBT was about 33% when the radiation dose was 185 kGy. The apparent reactions for the removal of DBT were presumed, and the corresponding kinetics equation was deduced and proven experimentally. Meanwhile, some methods were preliminarily used to improve the removal of DBT in the presence of gamma irradiation at room temperature. Among which, the mixture of hydrogen peroxide (H2O2) and acetic acid (HAC) appeared to be synergic to the radiation removal of DBT. Also, Cobalt-oxide showed significant promotion to the removal of DBT under the irradiated situation, and the removal efficiency increased by over 40% compared with radiation only.