Abstract: The influences of temperature, pressure, catalyst content, H 2O 2 content and mol ratio of propylene to H 2O 2 on epoxidation of propylene with H 2O 2 over TS-1 in a small-scale three phase loop thermosphonic reactor were investigated. The proper reaction condition was determined as follows: mol ratio of propylene to H 2O 2 was 1.1—1.3, temperature was 30—45?℃, reaction temperature rise was below 15?℃, pressure was 0—0.1?MPa, catalyst content was 3%—6%,and H 2O 2 content was 3%—5%.The conversion of H 2O 2 is above 94%,and selectivity of propylene is up to 96%. At these conditions, the yield of PO is higher than a figure of about 80%,which is achieved using conventional reactor. This reactor can realize catalyst regeneration continuously. This viable reactor can also be applied in other oxidation processes using TS-1, i.e. hydroxylation of phenol, ammoxidation of cyclohexanone.The results will lay a foundation for the development of the reactor in propylene epoxidation process.