Multi-layer graphene (MLG) films have been deposited on nickel film employing chemical vapor deposition (CVD) technique and oxygen plasma-based treatment method is introduced to tune the properties of MLG films after the transfer process. A MLG of 32 nm (~ 90 layer) was reduced to 12 nm (~ 30 layer) in 60 s with sheet resistance of 550 Ω/□ and transmittance of 83%. The geometrical dimensions, optical transmittance and sheet resistance evolution of the films during the treatment process are investigated. The method suggested in this paper yields controllability of the MLG film thickness and the electrical and optical properties after the transfer process and device fabrication, which has great potentials for transparent conductive electrode applications.