Abstract: The self-assembly behavior of a novel amphiphilic copolymer, poly(4-vinylpyridine)-b-poly6-［4-(4′-butyloxyphenylazo)phenoxy］hexyl methacrylate (P4VP-b-PAzoMA), was investigated in aqueous media. The morphologies and structures of aggregates were studied by means of Transmission Electron Microscopy (TEM), Laser Light Scattering (LLS) and UV-Vis spectrophotometer. Results showed that the aggregates with various morphologies were prepared by tailoring the initial concentration, solvent and pH value. The reversible tran-cis isomerization behavior of aggregates was observed by UV-Vis irradiation. The isomerization rate decreased with the increasing of the copolymer concentration. Besides, the red shift of absorption peak of azobenzene moieties was obtained by increasing the solvent polarity.