Stilbazolium dimers were designed and synthesized in which methylene groups of different lengths link the two chromophores. The second-order nonlinear optical property has been detected from their Langmuir-Blodgett monolayers. Photocurrent generation as well as other photophysical properties such as absorption and fluorescence were investigated. Comparing the dimers, with the stilbazolium monomer, we found strong second harmonic generation (SHG) signals and remarkable enhanced photoelectric conversion (PEC) quantum yields from 1.3-Bis [(E)- 4-(2-(4-(N-methyl, N-octadecylamino) phenyl) ethenyl) pyridinyll-alkane dibromide (B3) and 1,5-Bis [(E)- 4-(2-(4-(N-methyf, N-octadecylamino) phenyl) ethenyl) pyridinyll-ulkane dibromide (135). The structures of the Langmuir-Blodgett films of these dyes are assumed. Although these dimers are center-symmetric (or quasi-center-symmetric) molecules, they can form the ordered non-center-symmetric (in normal direction) monolayer by the compress force and the molecular interaction between the amphiphilic dye molecules and the water molecules at the air/water interface, The influences of bias, donor/acceptor, soluble oxygen, and light intensity to photocurrent generation were studied our results provide a new perspective to improve the performance of functional molecular material without any change Of the chemical structure of the chromophore itself.