The effect of doping Al2O3 on the Pb0.6Ba0.4ZrO3 thin films was investigated. With increasing Al2O3 content, the dielectric constant, tunability, and dissipation factor decrease while the figure of merit (FOM) increases. After doping with the optimal content of 1.5 at. % Al2O3, the Pb0.6Ba0.4ZrO3 films have a dielectric constant of 190, a tunability of 30%, a dissipation factor of 0.0067, a FOM value of 49, and a temperature coefficient of capacitance value of 1.13×10-4. The loss mechanism is discussed in order to provide information, which could be useful for further improvement of the material performance.