The　phosphorus　(P)　modified　MoO3-Bi2SiO5/SiO2　catalyst　was　prepared　by　a　simple　co-impregnation　method　and　investigated　in　the　epoxidation　of　propylene　by　molecular　oxygen.　The　catalyst　was　characterized　by　X-ray　diffraction　(XRD),　N-2　adsorption-desorption　analysis,　NH3-temperature-programmed　desorption　(NH3-TPD),　transmission　electron　microscopy,　and　Raman　spectroscopy.　It　was　found　that　the　P-modified　MoO3-Bi2SiO5/SiO2　catalyst　with　a　P/Mo　molar　ratio　of　0.5　exhibits　the　best　catalytic　performance　for　epoxidation　of　propylene　by　O-2,　the　TOFs　for　propylene　oxide　(PO)　formation　was　four　times　higher　than　that　of　the　unmodified　one　at　633　K.　The　modification　by　P　could　promote　the　dispersion　of　MoO3　nanoparticles　and　increase　the　number　of　weak　and　moderate　acid　sites　with　respect　to　the　phosphorus-free　MoO3-Bi2SiO5/SiO2　catalyst,　which　were　beneficial　to　the　formation　of　PO.　Moreover,　the　introduction　of　P　also　could　protect　the　mesoporous　structure　by　inhibiting　the　formation　of　Bi2Mo3O12,　which　was　beneficial　to　the　dispersion　of　active　species.　We　suppose　that　the　phosphorus,　bismuth　and　molybdenum　species　of　P-modified　MoO3-Bi2SiO5/SiO2　catalyst　play　important　roles　for　propylene　epoxidation　by　molecular　oxygen.