Abstract: A gas turbine blade was selected as the research object, based on finite element simulation. Firstly, the stress analysis was conducted on the non-cracked blade to determine the dangerous area, then the initial crack was set up in the dangerous area, and the structural integrity assessment was conducted based on the R6 specification for the cracks to draw the failure assessment diagram (FAD) and calculate the maximum acceptable crack size. Further, the influence of crack location assessment was investigated, and the influence of the existence of the second crack on the failure of the first crack was analyzed for the double cracks that may occur under actual working conditions. Finally, the effect of crack shape on FAD was examined. Results show that the maximum acceptable size of the 1/4 rounded corner crack is the smallest at both chamfers and the largest at the center. The presence of the second crack increases the danger of the first crack. When changing the crack shape, for a single 1/4 ellipticalcorner crack, the failure assessment curve gradually shifts from the safe region to the hazardous region with the increase of a/c (a is the length of the elliptical short half axis, c is the length of the long half axis), and the maximum acceptable crack size decreases.