Abstract: The ball head pin of the connecting rod of an automobile stabilizer bar fractured. The fracture causes were analyzed by means of macroscopic observation, chemical composition analysis, scanning electron microscope analysis, metallographic examination and hardness test, and further analyzed by finite element analysis. The results show that the mechanical properties of the ball head pin were reduced without quenching and tempering heat treatment, and the ball head pin was broken under the action of external alternating load.