A Reversed Duckweed polymeric LB film was fabricated by a new kind of amphiphilic polymer which was composed of hexanediamine- epichlorohydrin hydrophilic network and hydrophobic chains containing p-nitroazobenzene groups. Reversible optical birefringence and dichroism have been demonstrated in this polymeric LB film, and this reversible birefringence and dichroism can be cycled many times without appearance of any fatigue and show very good stability.