Abstract: This investigation is to determine the effect of temperature on bonding strength, impedance and power of PZT transducer in thermosonic bonding process. The results show that, too low less than 60 ℃ or too high more than 300 ℃ temperature can lead to unsucessful bonding or low bonding strength. A suitable temperature window is 200 ℃ to 240 ℃, which can lead to about 20 g bonding strength. As for the recommended production specification average value 5.4 g for 25 um diameter wire used, the available bonding window is 120 ℃ to 360 ℃. Moreover, for the fixed power setting of PZT transducer, the temperature change can lead to difference in actual power and impedance of PZT transducer. These experiment phenomena and analyses can be used for bonding parameters match and optimization in thermosonic bonding.