Abstract: The size distribution and morphology of dioctadecyl dimethyl ammonium chloride (TA-100) aggregates in aqueous solution were studied by means of dynamic light-scattering (DLS), transmission electron microscopy (TEM), and rheology. Polarizing microscope (PLM) was used to observe the texture of anisotropic liquid crystal formed in TA-100 aqueous solution. The results show that the average size of surfactant aggregates and rheological property of aqueous solution varies with surfactant concentration. Two relatively long hydrophobic chains of TA-100 lead to strong hydrophobic interaction, and the corresponding lamellar liquid crystal generates at lower surfactant concentration.