Layered manganese oxides with basal spacings up to 38.1 Angstrom have been synthesized by a facile novel method in which cationic surfactant CTAB directly reacts with (MnSO4H2O)-H-. and NaOH. The as-synthesized samples have expanded birnessite-type layered structures characterized by powder XRD and TEM. Synthetic parameters that are important to the formation and the basal spacing of the layered mesostructures are investigated, including the surfactant concentration, OH-/Mn2+ ratio, CTAB/Mn2+ ratio and aging time. Mechanisms based on self-assembling are discussed.