Abstract: 2195 Al-Li alloy plates with 8 mm in thickness were welded by friction stir welding,the influence of the stir pin shape on the welding quality of the joint was analyzed,the effects of welding parameters on the surface appearance of the joint were analyzed and the mechanical properties of the joint were tested. The results show that well performance of the joint could be obtained when the stirring head was the shape of the taper screw thread with three cants. At the temperature of-196 ℃ and the room temperature,with the increase of the welding speed,both the tensile strength and the elongation rate firstly increase to a maximum value and then decrease. At the welding speed of 100 mm/min,the tensile strength and the elongation reach the maximum value at the both low temperature（-196 ℃） and room temperature,the tensile strength of the joint are 428 MPa and 538 MPa,and the elongation rate are 4. 9% and 7. 4%. The fracture location of the joint is located in the heat affected zone,the fracture produced on the plane at an angle of 45° to the tensile loading direction,and the fracture surfaces showed a ductile failure with visible neck along the thickness direction.