Due to the manufacturing defects,fatigue and corrosion,the inner wall of the buffer hydraulic cylinder will produce axial cracks during the service process,which seriously affect the structural strength,buffer performance and service life of the hydraulic cylinder.The buffering system model was established by AMESim hydraulic simulation platform to simulate the actual working condition,and the buffering oil pressure was taken as the initial load for finite element analysis.The finite element model and crack growth model of buffer cylinder were established to study the effects of different initial crack shapes and crack locations on the fatigue life,and the dynamic stress intensity factor and crack morphology of crack front were analyzed.The results show that the cylinder without defects can fully withstand the buffer pressure.When the initial crack length is fixed,the leading edge stress intensity factor will increase and the crack growth speed will be accelerated with the increase of the depth-length ratio.The initial cracks with different depth-length ratios tend to propagate faster in the length direction after multiple cyclic loading.The fatigue life of cracks is different at different positions in cylinder,and the fatigue life of cracks is the shortest at the corner position with small wall thickness.