The effect of Ni content, film thickness, Ar pressure upon the magnetic and magneto-optical (MO) properties are studied with the (CoPt3)(1-x)Ni-x (x = 0-0.5) alloy films. Experimental data indicate that Ar pressure greatly affect the Kerr rotation angle during the blue-wave range. For the studied (CoPt3)(1-x)Ni-x alloy films, the satisfactory thickness for obtaining large perpendicular magnetic anisotropy is 42 nm. During the red-wave range, Ni addition almost has no effect on the potential figure of merit (PFOM), however, Ni addition (x approximate to 0.5) may induce satisfactory perpendicular anisotropy and coercivity. Although Ni addition reduces the Curie temperature, it also reduces the PFOM in the blue-wave range.