Pt1-xMnx/Co multilayers were prepared by magnetron sputtering. The crystal structure was analyzed by large and small angle X-ray diffraction. The relationship between structure and magnetooptical properties of PtMn/Co multilayers was studied. By measurement and analysis, the Kerr spectrum, Kerr ellipticity spectrum and Kerr loop show the Changing rules with the increase of doped Mn concentration. The physical mechanism was discussed.