The　effects　of　NaBr　on　the　adsorption　of　alkanediyl-bis-(dimethyl　dodecyl-　ammonium　bromide)　(referred　to　as　C12-s-　C12　2Br)　at　the　air/water　interface　and　on　the　micellization　in　the　solution　have　been　investigated　by　surface　tension　and　fluorescence　techniques.　The　results　showed　that　the　addition　of　NaBr　greatly　enhances　their　efficiency　and　effectiveness　in　surface　tension　reduction　as　well　as　the　ability　of　micellization,　even　induces　strong　premicellar　aggregation　before　the　cmc.　These　were　attributed　to　the　unique　molecular　structure　of　gemini　surfactant,　where　the　flexible　polymethylene　chain　was　the　spacer　linking　the　two　quaternary　ammonium　heads.　By　a　short　spacer,　the　charges　of　the　two　quaternary　ammonium　head　groups　are　concentrated.　Even　for　a　long　spacer　(s　=　12),　since　it　is　bent　toward　the　alkyl　tails,　the　similar　effect　is　also　produced.　This　results　in　the　high　sensitivity　of　their　ionic　head　groups　to　salt.　Besides,　the　addition　of　salt　also　effectively　promotes　the　hydrophobic　interaction　between　the　alkyl　tails　of　gemini　surfactants.　©　Springer-Verlag　2009.