With　p-N,N-dimethylaminobenzonitrile　(DMABN)　as　probe,　the　variations　of　the　intensity　of　its　second　fluorescence　emission　(Ia)　and　the　corresponding　characteristic　wave-length　(λa)　with　the　surfactant　(dodecyltrimethyl-ammonium　bromide　C12TABr,　quaternary　ammonium　Gemini　surfactant　C12-3-C12·2Br　and　sodium　dodecylsulfate　SDS)　concentration　(c)　in　NaBr-containing　or　n-C4H9OH-containing　aqueous　solution　were　measured　by　a　Hitachi　F4500　fluorescence　spectrophotometer.　The　results　showed　that　the　break　point　on　the　Ia-c　curve　and　the　minimum　of　the　derivative　variation　corresponding　to　the　λa-c　curve　agreed　well　with　the　critical　micelle　concentration　(cmc)　of　the　surfactant.　This　extends　the　range　of　DMABN　as　probe　to　measure　the　cmc　of　surfactant.　©　Editorial　office　of　Acta　Physico-Chimica　Sinica.