The ratio of non-magnetic to magnetic atoms was adjusted from 3:1 to 1:1 within the (Pt3Co)1-xNix system by sticking Ni chips to the Pt3Co target. X-ray diffraction and magnetic results showed that perpendicular magnetic anisotropy was not caused by texture at least in the Ni content range of 0.33—0.50. Furthermore, the effect of the Ni addition to the CoPt3 alloy films on their magnetic and magneto-optical propertical were investigated. The result shows that satisfactory Curie temperature TC, cohercivity Hc and Kerr rotation can be simultaneously obtained by selecting suitable Ni content (x=0.43) in the (Pt3Co)1-xNix system. This work provides an experimental basis for the application of PtCoNi alloy films.