Abstract: In order to widen the application of the engineering method of EPRI,with a series of analysis on the 3D elastic and elastic-plastic fracture mechanics finite element,the crack open displacements（COD）of cracked pipe were calculated and a key influence function h₂ in EPRI engineering method was studied against the COD results of FEM.A calculation method of h2 under the condition of tension and bending combined load was introduced in detail.In order to validate this method,the calculated h₂ results were compared with that of EPRI,and the calculated COD results based on the h₂ results were compared with that of PICEP.The compared results indicated that the calculated h₂ results as well as the COD results and the corresponding reference values were respectively accordant,and the calculation method in this paper was validated accordingly.