An ultrathin nanoscopic multilayer Mill has been fabricated through the electrostatic layer-by-layer self-assembly of water-soluble porphyrin derivative 5,10,15,20-tetrakis-(3,4,5-trihydroxy-phenyl)-porphyrine (DHP) and oppositely charged poly{(2, 5-bis (3-bromotrimethylammoniopropoxy)-phenylene-1, 4-divinylene)-alt-1, 4-(2, 5-bis (2-(2-hydroxyethoxy) ethoxy))phenylenevinylene} (BH-PPV). UV-vis spectra showed a continuous and uniform deposition process of BH-PPV and DHP. The film structure was characterized by small-angle X-ray diffraction measurement. The nonlinear optical property of ultrathin film was characterized by Z-scan technique with laser duration of 8 ns at the wavelength of 532 nm. The BH-PPV/DHP film exhibited nonlinear saturated absorption and strong self-defocusing effect. The nonlinear absorption coefficient and refractive index of the film sample are - 1.9 x 10(-5) m/W and - 5.57 x 10(-12) m(2)/W, respectively. (c) 2005 Elsevier B.V. All rights reserved.