Abstract: The linear defects of a number of 1Cr11Ni2W2MoV stainless steel bearing caps were studied,and the defects were detected and analyzed from the macroscopic and microscopic points of view.The results showed that the linear defects of the bearing caps were forging folding defects,and the formation reasons were mainly related to the extrusion of blank burrs and the deviation of the beating position during the multi-fire forming process.On this basis,the forming mechanism,harm and preventive measures of forging folding are expounded.