Abstract: The weldability test of 4 mm forged ZK60 magnesium alloy was carried out by using friction stir welding.The influences of the shoulder size,rotation speed and weld speed on the quaity and tensile strength of the weldiny joints were investigated.The optimized welding process parameters were obtained.The results show that the tensile strength increased with the increase of the rotation speed,but first increased and then decreased with the weld speed increasing when other parameters were the same.Under the conditions of the stir head with 15 mm in shoulder diameter,the rotation speed of 1 170 r·min-1 and the weld speed of 36 mm·min-1,a joint with smooth apperance,without crack,cavity,porosity and incomplete penetration or other defects could be obtained ,and the tensile strength could reach the peak value of 271.2 MPa,as much as 85% of that of the base alloy.