In order to reveal the effects of reduction and feed amount on the surface quality of forgings during the stretching,and to establish a criterion judging the occurrence of stretching folding,a stretching model of 5CrNiMo die block forgings is constructed by means of the FEM software DEFORM- 3D,and the effects of the reduction- to- feed amount ratio (namely the M value) on the maximum folding corner and the folding depth are discussed.It is found that the stretching folding occurs at a critical M interval of 0.8 ～1.0.On this basis,a criterion to judge the occurrence of folding during the stretching is established,that is,the folding of forging surfaces can be avoided when M is less than the range of 0.8 ～1.0,while the folding occurs when M is within or exceeds the range of 0.8 ～1.0.