Three point bending test of 2A50 forging aluminum was performed,and fatigue specimens of different crack growth stages were obtained,surface crack growth behavior was analyzed by scanning electron microscopy(SEM).CT observations of different crack growth stages were performed by offline micro-computed tomography,image registration of CT images in different crack growth stages were carried out,the problem of the position alignment of CT images in different stages was solved,and the comparison of crack growth was analyzed.A crack growth surface with single pixel thickness was obtained by extracting the intermediate surface of the final stage of the crack body,the crack bodies of different stages were projected onto the surface in turn,incremental graph of fatigue crack growth surface with single pixel thickness was obtained,and quantitative analysis of crack growth length was performed.