In this paper, the J-integral path-independence of a notch under incrementaltheory. the possibility of measurement of notch J. integral fracture toughness, and the equality in numerical values between the notch and the crack J-integrals. are investigated and demonstrated by means of elastic-plastic finite element analysis. Based on this. the authors deem that the J-integral may also play the role of a main parameter for notch elastic-plastic fracture analysis. Meanwhile. based on the notch J-integral numerical calculation. the authors further establish the notch failure assessment curve, and therefore investigate the dependence of the failure assessment curve on the dimension and geometry profile of the notch end and the feasibility of the R6 (third edition) failure assessment curve in the notch assessment. The method of the failure assessment diagram should be regarded as a simple and convenient engineering failure assessment approach for notch elastic-plastic fracture analysis, which can give the possible failure mode of the notch. The notch fracture toughness, JA, is no more a simple material constant. The engineering estimation method for the notch fracture toughness is expounded in this paper. which should lay the foundation of application of the notch failure assessment diagram.