Gaining　increased　attention,　the　problem　of　the　computer　viruses　has　attracted　lots　of　security　models　to　solve,　most　of　which　are　not　effective.　There　are　two　main　reasons.　1)　Some　of　them　can　not　stop　the　viruses　from　running.　2)　Antivirus　database　updates　may　cost　a　long　period.　This　paper　proposes　a　new　immune　model　called　self-immune　model　(SIM)　with　the　main　purpose　of　stopping　the　viruses　from　running.　SIM　checks　the　integrity　of　executable　codes　before　the　codes　being　executed　by　querying　the　security　strategy　database　(SSD).　If　the　integrity　is　broken,　SIM　will　stop　the　execution.　The　most　important　thing　is,　the　trust　process　tree　(TPT)　model　can　realize　the　dynamic　SSD　management.　With　these　measures,　SIM　enhances　the　security　and　do　no　harm　to　the　performance　of　OS.