在不同表压下制备芪盐的单层ＬＢ薄膜，测量ＬＢ膜的二次谐波信号．在低表压得到增强的二次谐波信号．对比芪盐的透射光谱，认为在ＬＢ膜中，芪盐以固相态存在，低表压时的固相态聚集体的吸收峰３５１ｎｍ使四阶非线性极化率ｘ（４）（－２ω；ω，ω，ω，－ω）产生共振增强，四阶光学非线性现象对二次谐波信号产生影响． A single layer LB film of stilbene salt was prepared under different gauge pressure, and the second harmonic signal of LB film was measured. The second harmonic signal is enhanced at low gauge pressure. Compared with the transmission spectra of stilbene salt, it is considered that the stilbene salt exists in the solid state at LB film. The absorption peak of the solid phase aggregate at low pressure is 351 nm, which makes the fourth-order nonlinear polarizability x (4) (- 2ω ; Ω, ω, ω, -ω) produce resonance enhancement, the fourth-order optical nonlinearity has an impact on the second harmonic signal.