Abstract: The driving voltage/current and response velocity of an ultrasonic bonding transducer were measured to obtain the dynamical characteristics of the ultrasonic vibration system. The response velocity of transducer was measured by the laser Doppler vibrometer. The loading and unloading process were analyzed and modeled in three segments. Experimental study shows that the square of velocity generally is associated with the energy of vibration.Unsteady status of a transducer can be represented by the vibration velocity after PLL start -up.The on/off of an ultrasonic generator is not an actual start/stop of the transducer that it is working with.Experimental results can be used to model a real ultrasonic bonder and optimize its functions.