Abstract: Some concrete agitation vehicle U type clip broke in use. By means of chemical composition analysis,macroscopic examination,mechanical property testing and metallographic examination,the failure reason of U type clip was analyzed. The result indicated,because the spring pad tight arriving,has not produced the crevice,the clamp position becomes less crowded,causes the shearing force which the U clip receives to increase,and the microstructure existence flaw,creates the early failure finally.