The effect of CO2 laser irradiation on the dielectric properties of PZT-4 ceramic is investigated. After laser irradiation, dielectric permittivity and dielectric loss of the ceramic decrease 5% and 60%, respectively, and the coercivity increases. The mechanism of the changes are analysed by Raman scattering, scanning electron microscope (SEM), X-ray diffraction (XRD) and the annealing process. It is shown that the microstructure changes of the irradiated sample mainly account for the dielectric properties. The CO2 laser irradiation could induce the tension stress, leading to the larger lattice parameter and the deviation of B site ion from the center of oxygen octahedron. The distortion of the oxygen octahedron results in the less activation of electric domains. Therefore, the polarization switching of the electric domains become more difficult, exhibiting the properties of "hard". This suggests that the laser irradiation may offer a new approach for the fabrication of lead zirconate titanate (PZT) based "hard martial" in several seconds without any ions addition.