The Langmuir-Blodgett (LB) film and the second-order nonlinear optical properties of a new azo compound were investigated by using means of second harmonic generation (SHG). Stable monolayer of 4-(carboxylic)-4-(amidogen)-azobenzene molecular formed on water surface could be transferred to solid substrate and built LB multilayers. The SHG signal intensity was very strong. The hyperpolarizability of the molecule was about 1.17×10-26 esu.