In present work, (Pb0.50Ba0.50)ZrO3 (PBZ) thin films doped by Mg from 0 to 5 mol% were deposited on Pt(111)/TiO2/SiO2/Si substrates by the sol-gel method. The phase structure of the Mg-doped PBZ thin films were characterized by X-ray diffraction. The electric-field and temperature-dependent electrical properties of the Mg-doped PBZ thin films were also investigated in detail. It was found that the Mg content had a strong influence on the dielectric properties of the thin films. The maximum values of dielectric permittivity and dielectric loss were obtained with 1 mol% Mg-doping PBZ thin films. However, the figure of merit (FOM) of the films was improved with increase in the Mg content.