A series of photoreactive polymers having cinnamoyl moieties with various flexible chain lengths as side groups were newly synthesized. The polymers were soluble in common organic solvents, producing a good quality of thin films in spin- and bar-coating and subsequent baking process. Their photoreactivity to UV light and photoalignment behavior were determined. And the polymers were evaluated as an orientation layer material to control the alignment of liquid-crystals on the film surface.