The epoxidation of propylene with hydrogen peroxide catalyzed by a reaction-controlled phase transfer catalyst (RCPT) composed of quaternary ammonium heteropolyoxotungstates in acetonitrile medium is studied. The influence of several factors on the reaction is studied, such as the reaction temperature, the effect of H2O amount, the reaction time, the effect of the catalyst amount, solvent effect and the recycle of the catalyst. Under mild conditions, H2O2 conversion is 98.6%, and propylene oxide (PO) selectivity based on H2O2 is 97.2%. During the epoxidation, the catalyst is dissolved in the solution. However, after H2O2 is used up, the catalyst can be recovered as a precipitate and can be recycled. We find that the recycled catalyst has similar catalytic activity as the fresh one.