100 bilayers 2-nitro-5-(N-methyl-N-octadecyl)aminobenzoic acid (NMOB) and cadmium arachidate (CdA) alternated Langmuir-Blodgett (LB) film was fabricated. The thickness of NMOB monolayer is 2.85 nm measured by small angle X-ray diffraction. It shows that NMOB molecule stands vertically in the alternated film. A DFT method, B3LYP, was used to calculate the energies of various conformations of NMOB with 4-31G* basis set. The computational results show that the tilted conformation is the most stable and the energy difference between this conformation and the vertical one is 31 kJ/mol. The refractive indices of NMOB/CdA alternated films were also determined at different wavelengths by waveguide measurement.