The structure properties of isotropic solution are studied with the electrochemical methods for SDS/ n-C4H9OH/H20 system. The measurements of the conductivity show that the isotropic range in the phase diagram is composed of three areas with different structures: OAV structure connecting with water corner, bicontinuous structure in the middle area and W/ O structure connecting with n-C4H9OH corner. This result has been proved by the measurements of eletrochemical diffusion coefficient. The middle phase microemulsion shows bicontinuous structure. The solubilization fraction of n-C4H9OH in SDS micelle is about 0.98.