Cationic　Gemini　surfactants,　alkanediyl-α,　ω-bis(dimethyl　dodecylammonium　bromide)　have　been　synthesized　by　the　following　method:　firstly　dodecyl　bromide　was　prepared　by　the　reaction　of　dodecanol　with　bromic　acid　in　the　presence　of　strong　sulfuric　acid.　Dodecylbromide　was　then　reacted　with　N,　N-tetramethyl　ethane　diamine(or　N,　N-tetramethyl　hexana　diamine)　to　prepare　the　title-compounds.　Micellization　of　these　Gemini　surfactants　was　investigated　using　conductivity　measurement.　The　results　showed　that　the　critical　micelle　concentration(cmc)　of　the　Gemini　surfactants　has　a　much　lower　value　compared　with　that　of　the　corresponding　＂monomer＂.　For　a　series　of　the　Geminis　with　the　same　length(s)　in　the　spacer　chain,　the　cmc　decreased　with　increasing　the　carbon　number　(m)　in　the　alkyl　chain.　The　aggregation　number(N)　of　the　micelle　also　drastically　decreased　with　m.　For　the　same　value　of　m,　the　cmc　varied　slightly　with　s,　which　indicated　that　the　electrostatic　interaction　between　the　ionic-groups　of　the　＂monomer＂　has　been　naturally　changed　duo　to　a　link　between　the　two　ionic-groups　of　the　＂monomer＂　through　a　spacer.　However,　N　was　strongly　decreased　with　s,　which　may　be　a　reason　of　steric　inhibition　coming　from　the　ionic-groups　due　to　a　link　of　spacer.　With　increasing　temperature,　micellization　of　the　Gemini　surfactants　was　slightly　enhanced.