Common　polyphenols　and　vitamin　C　in　food　are　particularly　unstable.　They　are　easily　oxidized　in　vivo　and　in　vitro,　which　will　affect　their　biological　activity.　In　previous　studies,　selenium　nanoparticles　(SeNPs)　were　used　to　load　and　improve　the　biological　activity　of　polyphenols.　However,　the　in　vivo　stability　of　these　SeNPs　is　still　unknown.　Selenium　nanoparticles　were　loaded　with　chlorogenic　acid　nano　selenium　(CGA@SeNPs),　gallic　acid-modified　selenium　nanoparticles　(GA@SeNPs),　and　vitamin　C-modified　nano　selenium　(VC@SeNPs)were　taken　as　the　research　subjects.　To　evaluate　the　stability　of　nano　selenium　with　different　surface　modifications　in　the　gastrointestinal　environment,　the　particle　size　changes　of　three　surface-modified　SeNPs　at　different　pH,　the　scavenging　rates　of　DPPH　free　radicals　and　ABTS　cationic　radicals　before　and　after　gastrointestinal　digestion,　and　the　retention　of　surface　modifiers　were　measured　by　simulated　gastric　digestion.　Results　showed　that　three　surfaces　modified　SeNPs　were　stable　under　acidic　and　neutral　conditions　but　unstable　under　alkaline　conditions.　After　gastrointestinal　digestion,　the　structure　and　content　of　CGA@SeNPs　were　the　most　stable.　Before　digestion,　CGA@SeNPs　had　the　best　antioxidant　activity　of　DPPH　free　radicals　and　ABTS　cationic　radicals.　After　gastric　digestion,　CGA@SeNPs　had　the　best　antioxidant　activity　against　DPPH　free　radicals,　and　the　optimum　antioxidant　activity　of　ABTS　cationic　radical　was　VC@SeNPs.　After　intestinal　digestion,　GA@SeNPs　had　the　optimum　antioxidant　activity　against　DPPH　free　radicals.　The　antioxidant　activity　of　ABTS　cationic　free　radical　of　CGA@SeNPs　was　at　the　top.　To　sum　up,　CGA@SeNPs　have　the　best　stability　and　antioxidant　activity　in　gastrointestinal　digestion.　©　2023　The　Author(s).