A series of poly(alkyl methacrylate)s having azobenzene and cyanobiphenyl moieties were synthesized and their optical properties were characterized. The effect of content of the photosensitive unit and the length of alkyl chain of a transparent unit on the photoresponsive alignment behavior was investigated. The azobenzene monomer (photoresponsive unit), the cyanobiphenyl monomer (mesogenic unit), and the alkyl methacrylate monomers with methyl, ethyl, n-butyl, hexyl or lauryl group (transparent unit) were copolymerized to yield transparent polymer films. Upon irradiation of LPL at 488 nm, a uniaxial optical anisotropy was generated due to the molecular alignment. The photoinduced alignment behavior was strongly dependent on the alkyl chain length and the intensity of the actinic light.