The degradation rates of pharmaceuticals contaminants (such as bezafibrate and carbamazepine) in the UV/S2O82- process at different Cl- concentrations (0.01, 0.1, 1.0, 10, and 100 mM) and pH values (3, 5, 7, 9 and 11) were investigated in this study. The degradation rate of bezafibrate showed an upward trend before the critical point (Cl- = 1.0 mM), the maximum enhancement was 51%, then the degradation rate decreased. The degradation rate of carbamazepine increased continuously, and the maximum enhancement was 66% when the a - concentration was 100 mM. The degradation rate of bezafibrate showed the maximum value at pH = 7 while the most rapid degradation rate of carbamazepine was observed at pH = 3. To explain these interesting results, a kinetic model was used to investigate the conversion of reactive radicals (such as SO4 center dot-, OH center dot, Cl-center dot, and Cl-2(center dot)-) at different Cl- concentrations and pH values. Simulation results showed that low concentrations ( < 1.0 mM) of Cl- transformed SO4 center dot- into OH center dot and Cl-center dot. With the further increased concentration of Cl- from 1.0 mM to 100 mM, OH center dot and Cl-center dot. can be converted into Cl-2(center dot-) Furthermore, Cl-2(center dot-) was the dominant reactive species when pH < 7, whereas OH center dot dominated when pH > 7. Few organic chlorinated products were observed in the UV/S2O82-/Cl- process, indicating that the reactions between bezafibrate/carbamazepine and the reactive chlorine radicals Cl-center dot/Cl-2(center dot-) occurred mainly through electron transfer and H-extraction, whereas the substitution reaction leading to the formation of organic chlorinated products was not dominated. This study positively demonstrated the absence of chlorinated product formation during SR-AOPs application.