The main reaction process of the HPPO (Hydrogen Peroxide to Propylene Oxide) method is to add methanol, propylene and hydrogen peroxide into the reactor containing the zeolite titanosilicate catalyst (TS-1) at a mass ratio of 4.2 : 1.3 : 1 for reaction. This process can enable 98% of the hydrogen peroxide to be converted, and the selectivity for propylene oxide can reach 95%. The small amount of propylene that has not fully reacted can also be recycled back to the reactor for reuse.