Abstract: The dynamic characteristics of piezoelectric ultrasonic transducer for IC packaging were studied based on finite element method (FEM)and experiment.With the help of ANSYS piezoelectric couple and nonlinear contact analysis function, the vibration characteristics of transducer in free and constrained states were analyzed respectively.The rule of ultrasonic energy transmission in spatial domain, time domain and frequency domain were discussed. Through modal analysis, the vibration modes of transducer were gained.The vibration information of transducer driven by sinusoidal voltage was obtained by use of harmonic response analysis.The transient response was figured out by transient analysis.The results show that the radial dimension and preload of bolt have influence on the modal distribution and dynamic characteristics of transducer.The frequency of voltage applied to piezoelectric stack affects the ultrasonic energy transmission.The relationship between the quality of bonding balls and the radial dimension of the bolt was studied through wire bonding test.The analysis and experimental results provide instructions for the design of transducer and the optimization of thermosonic bonding process.