The accuracy of reliability calculation was improved in the derivative sfem method . the local derivatives of fem and numerical method were used to obtain the iterative formulas of the performance function ' s local derivatives . the procedure is relatively simple and adaptable to engineering application as the stiffness matrix formed and decomposed only once 偏导sfem可靠度法求解构件疲劳可靠度，可靠度计算精度得到改善，通过有限元求偏导，结合数值微分技术，推导出了功能函数的偏导迭代格式，只需一次形成和分解总纲，计算较简便，适合工程应用。
