Abstract: To explore the effects of He ion irradiation on electromechanical behavior of PZT ceramic and micro-actuators, He ion irradiation experiments with three different total doses have been performed on PZT ceramic. By combining nano-indentation experiments and finite element analysis, anisotropic elastic parameters of PZT materials have been identified. The corresponding piezoelectric and dielectric constants are obtained with use of electronic test instruments. Based on the material parameters, deformation response and natural frequencies of the micro-actuators are calculated by finite element analysis, and the resulting irradiation effects are assessed.   With   increasing magnitude of total doses, the elastic, piezoelectric and dielectric constants of PZT ceramic show a decrease to some extent, with decay rates less than 10%, 4.8% and 16.6%, respectively. Variation of the maximum deformation and tensile stress of micro-actuators is less than 4.6% and 5.4%, respectively. The natural frequencies of micro-actuators vary less than 1%.