The geometry,electronic absorption spectra and second-order nonlinear optical properties of unsymmetrical liquid crystalline dimmers with imine and cholesteryl moieties were studied at the level of B3LYP/6-31G. The results showed that the maximum absorption electronic transition of the title compounds were from the highest occupied molecular orbital to the lowest unoccupied molecular orbital (π→π*),and the maximum absorption wavelength was in 337-349 nm,belonging to the UV. Decrease of central soft spacer length and increase of the attraction electron capacity of the terminal substituent group can enhance the second-order optical properties of the title compounds.