A reversed duckweed polymeric LB film was fabricated by a new kind of amphiphilic polymer which was composed of hexanedlamine-epichlorohydrin slightly crosslinked hydrophilic network and hydrophobic chains conatining p-nitroazobenzene group. This amphiphilic polymer can form stable liquid-condensed monolayer and be transferred as Z-type polymeric LB films. This LB film combines the order and mobility and it has a well-estab- lished layer structure and azo chromphore is in an isotropic state in each layer. Optical birefringence and dichroism can be laser induced and erased and this reversible birefringence and dichroism can be cycled many times without appearance of any fatigue and show a very good stability. On the basis of photo-induced optical blrefringence and dichroism, it is greatly anticipated that this polymer thin films bearing azo groups can be used as advanced materialsfor optical information storage.