Abstract: Experiment of flat butt-welding is conducted on the 2195 Al-Li alloy with 2 mm thickness using conventional TIG and ultrasonic assisted TIG welding process. The microstructural observation and mechanicaltesting were conducted on the welding joints. The results show that there is denser microstructure in the ultrasonic assisted TIG welded zone due to the effect of ultrasonic treatment. Besides, the equiaxed fine grain zone near the fusion zone in ultrasonic assisted welded jont is wider. The mechanical testing show that the ultrasonic assisted TIG welding joints have good mechanical properties whose strength coefficient is 6.7% higher than conventional TIG welding, and the percentage elongation after fracture increased by 1.36%. The fracture of the joints is in the hard brittle grain boundary phase of the heat affected zone. The microhardness test shows that the ultrasonic assisted TIG joints have a narrow heat affected zone.