Amphiphilic polymers bearing azobenzene groups (HRG-g-(NPH)n) were synthesized by means of grafting. The polymers can for in the "Reversed Duckweed" type monolayer at the air/water interface. Their behaviors in monolayers at the air/water interface were studied. The relationship between the chemical structure of the polymers and their behavior at the air/water interface was discussed. The order and stability of monolayers were determined by graft degree. The UV-visible spectra of this kind of polymer in solution and in LB films were explained by the molecular exciton theory. The orientation of mesogen groups incorporated in the LB film was studied by means of polarized UV-visible spectra, and the layer structure of LB films was studied by X-ray diffraction. A possible schematic model was proposed to describe the relationship between the structure of the LB film and that of this kind of polymer.