W e consider the thermo-magnetic properties of charged boson gas confined in a quasi-two dimensional harmonic superimposed by external magnetic field in the z-direction. A modified semi-classical approximation, which is the density of state approach, is used to calculate the magnetization and magnetic susceptibility for this system. Our approach enabled to consider the finite size correction. We get remarkable magnetic properties. The system shows diamagnetic behavior. The finite size effect decreases the transition temperature.