介绍了国内外七种Ｄ级抽油杆用钢的疲劳门坎值的测定。结合对抽油杆各特征部位半椭圆裂纹应力强度因子Ｋ的有限元计算，用断裂力学方法估算了各特征部位允许存在的裂纹尺寸。结果表明，允许裂纹深度α与使用应力σ之间存在有α＝Ａ／σ的关系。当抽油杆的抗拉强度符合ＡＰＩ规范１１Ｂ规定的σｂ＝７９３～９６５ＭＰａ时，七种材料的门坎值基本相同。当使用应力在疲劳极限附近处为３７２．６ＭＰａ时，抽油杆杆体表面存在有深度为０．１３～０．２７ｍｍ的裂纹，杆头锻方处存在有深度为０．６０～１．０２ｍｍ的裂纹，这些裂纹均不会扩展。 The fatigue threshold value of seven D-class sucker rod steels at home and abroad is introduced. Based on the finite element analysis of the stress intensity factor K of the semi-elliptical crack in each characteristic part of sucker rod, the crack size allowed by each characteristic part is estimated by fracture mechanics method. The results show that α = A / σ exists between the allowable crack depth α and the working stress σ. When the tensile strength of the sucker rod meets the σb = 793 ~ 965MPa as specified in API Specification 11B, the threshold values ​​of the seven materials are basically the same. When the stress is 372.6MPa near the fatigue limit, there is a crack depth of 0.13 ~ 0.27mm on the rod surface of sucker rod. There is a depth of 0.60 ~ 1.02mm Cracks, these cracks will not expand.