Polyamic acid derivatives containing photosensitive azobenzene units in their main chain have been synthesized. Y type polyamic acid LB films were fabricated which were then converted into the polyimide LB films by chemical imidization accompanied by the elimination of long alkyl amines. The orientation of the polymer chains to the dipping direction was observed by the orientation of the chromophore in the plane direction, which depends strongly on the structure of the diamines. Aromatic diamines lead to a preferential orientation parallel to the dipping direction, while aliphatic diamines did not result in a preferential orientation, The reversible photo-isomerization was caused by both the polyamic acid and polyimide LB films. The rigid aromatic polyimides showed less reactivity compared with the more flexible aliphatic polyimides.