Abstract: Stress intensity factor of surface crack front under biaxial-bending loading was calculated by FRANC3 D.The results of simulation and theoretical calculation are totally consistent.Besides,stress intensity factor of surface crack front of various aspect ratios in the case of equal area crack is analyzed.It is found that,ellipse surface crack with a/c = 1 /3 is mostly dangerous if the surface crack is shallow; ellipse surface crack with a/c = 2 is mostly dangerous if the surface crack is deep.