Abstract: According to the structural characteristics of boom of mechanical excavator boom, through the statics analysis with ANSYS workbench software, the position of crack generation determined; the propagation of semi-ellipse crack is imitated on the structure surface of boom with the method of finite element, stress intensity factor range of different crack length obtained and its function relationship with crack length matched. According to the Paris formula of fatigue crack propagation theory, the life of boom from the crack generation to the critical length of the crack under the single influence of a certain alternating load Δσi is obtained. Finally, recombining the stress—time history at the hazardous position of boom obtained from the automatic dynamic analysis of mechanical systems (ADAMS), the crack growth life of excavator’s boom is worked out on the basis of Miner rule.