Abstract: The process of aluminium alloy spot welding is widely used nowadays and the industry puts forward higher request in its properties and quality.The microstructure of aluminium alloy spot welding nuggets decides its macroscopic properties.In this paper,the microstructure of nugget was changed to enhance its properties and quality.Carbon nano-tube(CNT) was chosen as the addition of the aluminium alloy spot welding,and further analysis of the mechanical properties,microstructure and components of the welding spot of aluminium alloy.The results indicated that when the CNT was added in the aluminium alloy,the sizes of spot welding grain decreased significantly.The CNT distributed uniformly in the nuggets and it could increase the hardness and intensity significantly.The further analysis indicated that the carbon nano-tubes strengthening mechanism was mainly dislocation multiplication,transformation of load,constrained deformation and fine grain strengthening.