In this paper, the study for the bonding tool position of ultrasonic transducers for thermosonic Flip-Chip LED bonding is presented. Improving the efficiency of ultrasonic transducers plays an important role in the bonding process. To obtain the actual movement of ultrasonic transducer, finite element method ATILA was employed to get more detailed information. To verify the reliability of simulation results, the impedance characteristic and resonance frequency of the transducer mechanical system have been measured using a LCR meter. Moreover, different mounting position of bonding tool on the transducer was studied. Use ATILA to find the best tool position, and vibration amplitude of the tool was measured by Laser Doppeler Vibrometer. Experimental bonding results are verified by in-house shear force test bed.