Photosensitive polyimide containing methoxy cinnamate derivatives as a photo-alignment layer is investigated. 4-Methoxy cinnamic acid, 2-methoxy cinnamic acid and 2,5-dimethoxy cinnamic acid were irradiated and the absorption spectra were obtained with irradiation time. 4-methoxy cinnamic acid and 2-methoxy cinnamic acid are observed isosbestic points at 258 nm and 250 nm, respectively and 2,5-dimethoxy cinnamic acid has no isosbestic pioint. 2-Methoxy cinnamic acid was most photosensitive with 30 sec irradiation time. Polyimide containing methoxy cinnamte derivatives was synthesized and the anisotropy of alignment layer was induced by irradiation linearly polarized UV (LPUV). UV irradiation of a film a of polyimide with 2-methoxy cinnamate proceeded predominantly by the photo-isomerizaiton.