Abstract: The bulk properties of the mixed aqueous solutions of cationic gemini surfactant 12-3-12, 2Br~- and conventional anionic surfactant SDS, and the effects of mixing ratio on the appearances, viscosity, electrical conductivity of the mixed solutions have been investigated. Results show that just as the conventional anionic and cationic aqueous solutions, present system can form liquid crystal and aqueous two-phase system (ATPS) under certain mixing ratio. Their unique properties are dependent upon the unique structure of gemini surfactant and the synergistic effect of Geminis and conventional surfactants. Moreover, the changes of mixing ratio have great effects on the viscosity, electrical conductivity of the mixed solutions. Results achieved by freeze etching technique, negative-staining technique and transition electron microscope show that the mixing ratio affects the microstructure of surfactant aggregates and thus leads to the variation of solution viscosity and electrical conductivity.