Abstract: Combining the actual running conditions, the cracking reasons of 5083 aluminium alloy brackets were analyzed by means of chemical compositions analysis, metallographic examination and fracture analysis. The results show that the high cyclic stress and the environment corrosion resulted in the fatigue cracking of the brackets. At the same time, many inclusions in the material accelerated the fatigue cracking. At last, structure improvement measure was proposed to ensure the product life.