Effects of organic solvent addition on the epoxidation of propene catalyzed by TS-1 were studied. It was found that addition of 1,2-dichloroethane to the reaction increased not only the conversion and utilization efficiency of H2O2, but also the selectivity to PO. The origin of the effects was studied through the characterization of the catalysts after the reaction and the influence of organic solvents on the decomposition of H2O2 and PO.