Glycine(Gly),　cysteine(Cys),　aspartic　acid(Asp),　leucine(Leu),　lysine(Lys),　and　methyl　amine(MA)　were　chosen　as　typical　nitrogenous　compounds,　and　the　effects　of　them　on　trihalomethanes　(THMs)　formation　and　chlorine　demand　were　performed　on　filtrated　water.　Results　show　that　the　nitrogenous　compounds　enhance　THMs　formation,　and　the　increased　levels　are　controlled　by　characteristics　and　the　concentration　of　nitrogenous　compounds.　The　increase　in　THMs　formation　follows　the　order　of　Asp(126　μg/L)＞Cys(119　μg/L)　＞MA(106　μg/L)＞Lys(97　μg/L)Gly(96　μg/L)＞Leu(80　μg/L)(while　nitrogenous　compounds=1.0　mg/L,　and　background　THMs=60　μg/L).　The　increase　in　chlorine　demand　is　approximately　proportionate　to　the　content　of　nitrogenous　compounds,　which　illustrates　that　the　increase　is　mainly　caused　by　the　reaction　of　nitrogenous　compounds　with　chlorine.　And　the　increase　in　chlorine　demand　follows　the　order　of　Cys(27.8　mg/L)＞Asp(22.6　mg/L)=Gly(22.6　mg/L)　＞Lys(21.6　mg/L)＞MA(14.1　mg/L)　＞Leu(11.8　mg/L)　(while　nitrogenous　compounds=1.0　mg/L,　and　background　chorine　demand=1.8　mg/L).　The　mechanisms　of　nitrogenous　compounds　enhancing　THMs　formation　are　summ　the　increase　of　chlorine　demand　raising　THMs　formation　in　reaction　of　NOM　with　chlorine,　and　the　THMs　formation　in　chlorination　of　nitrogenous　compounds　themselves.