A new type of dimeric cationic surfactant was synthsized from dodecylamine,its hydrochloride and epichlorohydrinor other spacers.The effects of different proportion,different solvents and temperature on the reaction rate and product are investigated.Meanwhile,the surface tension,crac and other characters are detected.The double quaternary ammonium salts had good water solubility.Its cmc is lower than common Surfactants by 1-2 order magnititude.It had strong foaming ability and good foam stability.