A salt-free cationic and anionic (catanionic) surfactant system was formed by mixing a double-tailed di-(2-ethylliexyl) phosphoric acid (DEHPA, commercial name P204), which is art excellent extractant of rare earth metal ions. with it single-tailed cationic trimethyltetradecylammonium hydroxide (TTAOH) in water. With the mole ratio (r) of DEHPA to TTAOH varying from 0.9 to 1, the phase transition occurred from it densely stacked vesicle phase (L-alpha v) to a lamellar phase (L-alpha l). Macroscopic properties, such as polarization and rheology, were measured and changed greatly during the Course of the phase transition. When r was 0.96 or 0.98, the steady state shear curves exhibited two yield stress values. indicating the coexistence of the L-alpha v phase and the L-alpha 1 phase. The L-alpha l phase formed in the salt-free and zero-charged system (r = 1.0) is defective and undulating, which was confirmed by cryogenic transmission electron microscopy (cryo-TEM). The deuterium nuclear magnetic resonance spectra (H-2 NMR) showed that a single peak (singlet) split into two symmetric peaks (doublet) gradually, indicating the phase transition from the L-alpha v phase to the L-alpha l phase. Correspondingly. phosphorus nuclear magnetic resonance spectra (P-31 NMR) presented changes in both the chemical shift and the peak width, indicating that these two types of bilayer structures are of different anisotropy degrees and different viscosities, When the L-alpha l phase is subjected to a certain shear force, it can be reversed to a L-alpha v phase again, which was proved by rheological, H-2 NMR, and P-31 NMR measurements. furthermore, a theoretical consideration about the formation of the defective and undulating L-alpha l phase was taken into account from a viewpoint of energy.