||The present study is aimed at the preparation of smectic guest-host polarizer. To accomplish this purpose, we designed and synthesized a new reactive liquid crystalline monomer containing two acrylate groups as the “host” material. The chemical structure of the monomer was characterized by 1H-NMR, FT-IR. The existence of smectic phase was confirmed by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). We fabricated “guest-host” system thin-film polarizer in the sandwich cell. The in-situ photopolymerization was carried out at room temperature in the smectic phase by irradiating UV light. The dichroic ratio(DR), order parameter(S) and degree of polarization(DOP) of the thin-film polarizer, where DR=20.7，S=0.87 and DOP=97.8%, were determined by polarized UV-vis spectroscopy, which is much higher than nematic thin-film polarizer.