Abstract: A liquid crystalline monomer，p-allyloxy benzoic acid p-hydroxy phenyl cyanogen ester，was synthesized using allyl bromide, p-hydroxybenzoic acid and p-cyano phenol as main material. New smectic sidechain liquid crystalline polysiloxanes were synthesized by addition polymerizations between liquid crystalline monomer and polysiloxanes. Liquid crystal monomer and liquid crystal polymer were characterized by FT-IR and 1H-NMR analysis. Liquid crystal behaviors of liquid crystal monomer and liquid crystal polymer were analyzed by DSC、POM and XRD. The hydrosilylation reaction reduced completely shows the mesogenic monomer and polymer are all interconverted to liquid crystalline. The fanshaped texture is formed due to smectic as heating up and cool down.