Based on the central composite experimental design method, the impact levels of uncertain parameters to failure assessment curve were qualitatively analyzed, such as material properties, defect dimension and operating pressure. With the sensitivity method, the impact levels of uncertain parameters to failure assessment curve were quantitatively analyzed. It is demonstrated that the qualitative results and quantitative results are consistent. Based on EPRI method, probabilistic failure assessment curves (PFAC) of commercially pure titanium TA2 were established with the probabilistic method, and non-probabilistic failure assessment curves (NPFAC) were established based on interval analysis method. Compared NPFAC with PFAC, it could be found that NPFAC for structural defect assessment is feasible and effective