Single-atom　catalyst　(SAC)　attracts　extensive　interest　in　heterogeneous　catalysis.　Although　single　metal　atoms　(M1)　can　serve　as　the　dominant　active　site,　growing　evidences　reveal　that　the　directly　coordinated　heteroatoms　usually　determine　the　geometric　and　electronic　structure　of　single-atom　center.　However,　the　impact　of　the　peripheral　environment,　not　bonded　to　M1,　is　in　its　infancy　while　plays　a　significant　role.　In　this　review,　we　survey　the　recent　progresses　of　optimizing　SAC　performance　through　modulation　of　the　peripheral　species,　either　by　influencing　the　main　M1　center　or　serving　as　additional　active　site.　Firstly,　we　introduce　the　basic　principles　of　single-atom　catalysis　and　the　role　of　the　peripheral　environment　in　modifying　catalytic　behaviors.　It　is　proposed　that　the　single-atom　site　constitutes　an　active　domain　with　the　microenvironment,　and　the　regulation　of　peripheral　species　within　this　active　domain　can　effectively　improve　the　catalytic　performance.　Subsequently,　the　design　strategies　and　characterizations　of　peripheral　environment　are　summarized.　The　peripheral　effects　on　thermal,　electro-,　photo-catalysis　and　the　underlying　reaction　mechanisms　are　then　elucidated.　Finally,　the　challenges　and　future　prospects　regarding　the　involvement　of　peripheral　species　in　SAC　are　put　forward.　This　review　underscores　the　significance　of　the　peripheral　environment　in　SAC,　which　can　provide　important　implications　for　the　enhancement　of　catalysis　through　peripheral　dopant　engineering.　©　2025　Elsevier　B.V.