Abstract: The copular axle for cutting rubber machine was broken when the machine was being used. It caused a fatal accident resulting in a worker endured. In fact,the total operating time of the machine was less than two months. The test and analysis were made by means of chemical composition analysis,mechanical properties testing,metallographic examination and fracture analysis. As expected,the analysis result was proved that it was the fatigue fracture. The analysis showed that the fracture of axle was caused by bending stress resulted from cutting course,though the shaft endured strength and press stress during its runing.