Prestressed　anchor　has　been　gradually　applied　to　the　construction　of　large-span　tunnel　surrounding　rock.　This　paper　aims　at　the　design　principle　of　prestressed　anchor　considering　the　bearing　arch　theory　of　surrounding　rock.　The　supporting　mechanism　of　prestressed　anchor　in　tunnel　engineering　was　investigated.　The　anchorage　section,　free　segment,　prestress　and　bearing　arch　axial　force　and　thickness　of　prestressed　anchor　were　analyzed　respec-tively.　Combined　with　the　engineering　background,　the　design　parameters　of　prestressed　anchor　were　calculated　theoretically.　Based　on　the　obtained　theoretical　results,　the　numerical　simulation　method　was　used　to　further　determine　the　influence　of　several　main　factors　such　as　anchor　length,　row　spacing　and　prestress　on　the　stability　of　surrounding　rock,　and　to　verify　the　effectiveness　of　the　theoretical　design　method　for　controlling　the　stability　of　surrounding　rock.　Furthermore,　a　case　study　of　the　Badaling　tunnel　was　introduced　to　illustrate　effectiveness　of　the　proposed　method.　The　final　monitoring　results　show　that　the　maximum　displacement　of　vault　settlement　is　20.35　mm,　which　is　far　below　the　control　standard　value.　This　study　can　provide　a　theoretical　reference　for　the　application　of　prestressed　anchor　to　control　large　deformation　of　surrounding　rock.