A novel ultrasonic vibration enhanced friction stir welding (UVeFSW) was employed to join the third- generation 2195-T6 Al-Li alloy, and the effect of ultrasonic vibration on microstructures and mechanical properties of the joint was studied. It is revealed that UVeFSW can enhance the plastic material flow to suppress the weld defects. The critical welding speed of sound joints is increased in UVeFSW compared with conventional FSW. When ensuring that the tensile strength of the joint is 75% that of the base material, the welding speed and efficiency in UVeFSW are higher than those in conventional FSW. Superimposing ultrasonic vibration can significantly enhance the mechanical properties of 2195 Al-Li alloy FSW joints at a higher welding speed. The maximum tensile strength of the UVeFSW joint is 449.5 MPa, which is 83.1% that of the base material. UVeFSW can increase the welding efficiency by increasing the critical welding speed and simultaneously ensuring the joint properties.