With　increasing　the　number　of　oxyethylene　groups　in　the　spacer　of　[C12H25N+　(CH3)(2)](2)C2H4　(OC2H4)(n).2Br(-)　(C-12-2-E-n-C-12.2Br,　n　=　2,　3),　the　homogeneous　regions　in　the　phase　diagrams　of　aqueous　mixture　of　C-12-2-E-n-C-12.2Br　with　C12H25SO4Na(SDS)　expand　obviously　in　comparison　with　that　of　[C12H25N+(CH3)(2)CH2](2).　2Br(-)/SDS　mixed　system.　There　exists　a　synergism　between　C-12-2-E-n-C-12.2Br　and　SDS　during　the　mixed　micellization.　The　minimum　critical　micelle　concentration　(cmc(T,　min))　in　the　homogeneous　region　is　0.0339　mmol.L-1　and　the　corresponding　molar　fraction　(x(2)*)　of　SDS　in　the　bulk　solution　is　0.447　estimated　by　Rosen　theory.　At　X-2　=　0.5,　the　corresponding　molar　fraction　(x(2)(M))　in　the　mixed　micelle　and　the　total　aggregation　number　(　N-T)　are　0.　43　and　36　respectively.