Effect　of　spacer　chain　length　on　aggregation　of　C12-S-C12　·　2Br　dimeric　surfactants　in　aqueous　solutions　has　been　investigated　by　using　conductivity　and　viscosity　measurements　as　well　as　steady　fluorescence　quench　technique.　The　results　showed　the　ability　for　the　micelle　formation　of　C12-S-C12　[Closed　Circle]　2Br　dimeric　surfactants　is　much　better　than　that　of　their　monomer,　dodecyltrimethylammonium　bromide　(C12TABr).　The　values　of　cmc　for　the　former　are　lower　than　an　order　compared　with　the　latter.　The　aggregation　number　N　of　C12-S-C12　·　2Br　micelles　decreases　with　increasing　concentration　c,　specially　for　s=2,　the　value　of　N　increases　rapidly　at　c＞7.　7　mmol/L.　The　calculated　result　indicates　a　significant　change　in　the　micellar　shape　and　the　formation　of　prolate　ellipsoid　micelles　at　c＞7.　7　mmol/L.　The　viscosity　measurement　for　C12-2-C12　·　2Br　micellar　solutions　demonstrates　the　calculated　results.