A simple strategy is presented for the construction of an electrochemical interface with tunable defects by the Pt supported self-assembled didodecylmethyl-ammonium bromide (DDAB) bilayer lipidlike membrane composed of a series of diluted nano-Fe3O4 dispersion precast on the Pt surface. It is speculated that the local rupture or collapse would occur in the DDAB self-assembling process when encountering the bulge site, nano-Fe3O4 particle precast, and hereby would induce sparse or dense defects in the membrane, and as a result, attain a tunable interface. The distribution morphology of the nano-Fe3O4 was characterized by atomic force microscopy. Cyclic voltammetry and ac impedance spectroscopy were performed to evaluate the electrochemical properties of the as-prepared interfaces by using Fe(CN)(6)(3-/4-) probe. For explanation of the tunable electrochemical properties of the interfaces, quantitative parameters of the defects were provided and relative theories of microarray electrodes were introduced into the study. It is concluded that the interfacial properties can be tuned from dielectric electrode to microarray electrode to conductive interfaces by the precasting nano-Fe3O4 dispersions. (C) 2004 The Electrochemical Society.