Abstract: In this paper, the effect of stiring pin rotation speed on mechanical properties of 2024-M joints of friction stir welding was analysed.The results showed that the fracture position of 2024-M joints varied with the rotation speed of stiring pin in the axial tensile experiment.A larger percent of block particles were reserved in the nugget zone with higher rotation speed, the properties of welding joints decreased and the fracture occured in stir zone.With lower rotational speed, the proportion of friction mechanism between the shoulder and top surface of welded material decreased.The layered metal flow was obtained at the rotational and traverse speeds of 600 r/min and 20 mm/min respectively, and it can become lower for welding joints again.The optimal welding parameters were the rotational and traverse speeds of 800-1 200 r/min and 20 mm/min respectively.Tensile fracture surface inclined at 45° to stress axis in base metal region, which is a shear fracture.