Abstract: The J-integral as a controlling parameter was applied to the crack growing process by Hutchinson and Paris. An engineering approach based on J-integral was proposed by some Ref. However, it is necessary to study whether the J-integral is really a basic controlling parameter. It has been shown from the results given in this paper that J-integral is not basic while the Jn-intergral defined in this paper is a basic controlling parameter for crack growth in elastic -plastic state.In this paper, a method combining experimental observation with elastic-plastic finite element numerical calculation is used to study the feature of J and Jn. It is shown form Equ.（20） that the essential feature of local stress/strain field can be characterized by Jn, but it can be seen from Equ（8） that J-integral includes the energy dissipated in geometry-dependent plastic deformation remote from the advancing crack-tip.Thus , Jn should be the basic parameter controlling crack growth, but J is not basic. Jn-integral may be the most promissing parameter for elastic-plastic fracture.