Abstract: Effects of ionic strength and ethanol content on the coordination structure of Cu(Ⅱ) complex of poly(4-vinylpyridine) partially quaternized by ethyl br-omide (EBQP₄VP) in aqueous solution were studied by riscometric, spectro-photometric, and electron spin resonance (ESR) techniques. Changes of ionic strength and ethanol content of Cu(Ⅱ)-polymer complexes lead to the conformation changes of the polymeric ligand chain. The structural changes in the coordination sphere of the Cu(Ⅱ)-polymer complexes were induced by the conformational changes of the polymeric ligand. Changes of the catalytic oxidation activity of hydroquinone may result from distortion of tetragonal symmefry of Cu(Ⅱ)-polymer complexes.