A series of Pt/Co/Pt/Ni modulated multilayer with Ni layer thickness tNi ranging from 0 to 2.4nm have been prepared by magnetron sputtering on Pt buffer. The relations between conductivity tensors σ1xx,σ2xx,σ1xy,σ2xy and tNi were calculated with measured values of Kerr rotation, ellipticity, refractive index and absorption index. And then, θK =θK σ1xx(tNi,σ2xx(tNi),σ1xy(tNi),σ2xy(tNi) as a compound function of tNi was calculated. It exhibits that, with the change of tNi, σ2xy is the major factor to influnce θK at short wave length and all of the four conductivity tensors are important at long wavelength, no one is negligible. We think that the splitting of Pt 5d band, which originates from spin-orbit coupling, decreases with the increase of tNi. The Curie temperature TC decreases monotonically with increasing tNi. For purpose of application, we show a range of tNi (0.3—1.0nm), in which TC is lower while θK and R is higher than pure Pt/Co multilayers.