Ferromagnetic resonance (FMR) was observed for Co82Pt12 films with various process. And relation between effective damping factor ( α eff ) and compositional modulation (CM) in the atomic layers, and other magnetic properties to investigate the relationship between local variation of the magnetic properties and the α eff . The CM was changed by the substrate temperature T sub and deposition rate of the Co-Pt alloy film. As a result, it was found that 1) For the T sub dependence, α eff took maximum value of 0.22 at T sub = 200 oC. 2) For the rate dependence, a eff linearly increases with 0.12 to 0.35 with increasing deposition rate from 0.3 to 2.0 nm/sec. 3) There was no similar tendency between a eff and CM for the Co-Pt alloy film with T sub and rate change. Thus the CM is not dominant factor of the a eff for the compositionally modulated Co-Pt alloy film.