The　anchimeric　assistant　mechanism　of　the　second　electrophilic　region　on　β-methylnitrosopiperazine　was　studied　by　using　ab　initio　and　density　functional　theory　(DFT)　method　with　the　6-311G　(d)　basis　set.　The　results　show　that　the　anchimeric　assistance　of　N　prime　atom　on　the　piperazine　ring　or　the　oxygen　atom　on　the　N　prime　-substituted　group　enhances　the　reactivity　of　β-methylnitrosopiperazine　metabolites,　which　can　be　used　to　explain　the　phenomenon　that　the　carcinogenicity　of　methyl　substituted　N-nitrosopiperazines　is　much　more　potent　than　that　of　their　parent　compounds.　This　research　provides　a　theoretical　evidence　for　the　formation　of　the　second　electrophilic　region　on　the　γ-positions　of　N-nitrosopiperazines　in　their　carcinogenic　metabolism.