An organic compound-stilbazium salt with large moleoalar hyperpolarizabllity was synthesized which can form molecular monolayer. The optical seoond-harmonio signal of the stilbazium salt monolayer was measured and the molecular hyperpola-rizability β was obtained, to be 1.2×10-27 esu. Unfortunately, it is difficult to fabricate stable multilayer of the stilbazium salt. We reported in this article the fabrication of mixed stilbazium salt/araohidio acid Langmiur-Blodgett (LB) films and the studies of their nonlinear optical properties, in order to explore the possibility of the mixed films in preparing the stable molecular multilayer structure with large second-order susceptibility. The experimental results showed that the mixing of two suitable compounds is a way to fabricate stable multilayer films with high nonlinear coefficients.