n - Octadecyl 4 - (4′-nitrophenylazo)-1 - naphthyl ether, ONNE, was synthesized and the optical characteristics of ONNE was studied. Noncentrosymmetric Z-type Langmuir-Bodgett (LB) films of ONNE were prepared and the second harmonic generation, SHG, intensity of the films were measured. The structural characteristics of floating monolayer and LB film of ONNE were discussed with the π - A isotherm, UV - visible absorption spectroscopy and ellipsometry. The polarized UV - visible absorption spectroscopy and SHG intensity suggest molecular orientation in LB film.