The phase behavior of the SDS (sodium dodecyl sulfate)/BA (benzyl alcohol)/H2O system is shown by the phase diagram, and the structures of the aggregates are determined by small-angle X-ray diffraction and cyclic voltammetry. The measurements of diffusion coefficients and diffusion activation energies of surfactant aggregates show that the L1 range is not an area of a single oil in water structure, but an area with three different structures: the rod structure, spherical structure, and the bicontinuous structure. The change between microemulsions and lamellar or hexagonal liquid crystal or inverse micelle can be explained by the R ratio theory.