Abstract: The environmental friendly preparation process of propylene oxide (PO) by propylene epoxidation with hydrogen peroxide was studied. Based on the results of basic research, laboratory test and side-line testing, a 1.0 kt/a pilot plant was built for PO preparation by epoxidation of propylene with hydrogen peroxide. Factors influencing the conversion of hydrogen peroxide and PO selectivity were investigated on pilot plant, using HPO-1 catalyst containing modified hollow titanium silicalite molecular sieve. The process conditions of pilot plant test were confirmed, in which the reaction temperature is 30—70 ℃, the WHSV of hydrogen peroxide is 0.12—1.20 h-1, the molar ratios of methanol to hydrogen peroxide and propylene to hydrogen peroxide are 5—25 and 1.2—2.5, respectively. Running under such conditions for more than 6 000 hours, the decrease of catalyst activity is nonsignificant, the conversion of hydrogen peroxide is 96—99% and the PO selectivity is 96—98%. By separating with dual azeotropic distillation process and purification, the purity of PO product is more than 99.97%.