According to the type of YC225LC-8 hydraulic backhoe excavator, mechanical analysis was carried out in three typical work condition of the working device by using the mechanical theory and method. The static strength finite element analysis of excavator boom was carried through by using ANSYS, from which, the stress and strain deformation contour diagrams of three typical work condition were obtained so that the hardness can be checked. The results of finite element analysis showed that the static intensity of the boom is enough. The maximum stress mainly occurred in the hinge point connected the boom cylinder with the boom and the hinge point connected the boom with the base, which played an important part in controlling the strength of the excavator working device. The study results are of certain guiding significance for working device’s optimization design.