Abstract: In order to investigate the influence of ultrasonic vibration on the temperature field of ultrasonic assisted friction stir welding of 6061 aluminum alloy, the contact interface friction coefficient model was established by analytical modeling, and the thermo-mechanical coupling finite element analysis model was established by numerical simulation. The temperature measurement experiment of ultrasonic assisted friction stir welding of 6061 aluminum alloy was carried out. By comparing the finite element analysis with the experimental results, it is found that the workpiece surface temperature distribution curve and sampling point temperature obtained by the analysis are basically consistent with the experimental results, which verifies the accuracy of the established model. The analysis results also show that ultrasonic vibration can change the friction state, reduce the welding friction heat generation, the peak temperature and the area of high temperature region. The effect of ultrasonic amplitude on welding peak temperature is more significant than frequency.