Abstract: Ultrasonic assisted friction stir welding (UAFSW) is a new technology of adding axial high frequency vibration on the mixing head of friction stir welding (FSW). The 7075 aluminum alloy with 6 mm thickness was used as the research object, and the heat source model of UAFSW and FSW was established, the influence of axial vibration on the temperature field and residual stress was investigated by ANSYS software. The results show that the addition of axial vibration can increase the heat input, increase the peak welding temperature and reduce the residual stress of the weld. When the vibration frequency is constant, the peak welding temperature and residual stress increase with the increase of vibration amplitude at the same rotating speed and welding speed.When the vibration amplitude is constant, with the increase of vibration frequency, the welding peak temperature and residual stress also increase correspondingly.