For large hydraulic excavator for mining higher product development costs and longer development cycle phenomenon, with a domestic largescale mining companies 125t hydraulic excavators for the study, its boom system was analyzed. 3D models of excavators and hydraulic system simulation model were built,cosimulation was carried out, and verified by experiment.Simulation and experimental results show that the simulation model can correctly simulate actual boom hydraulic system, dig hydraulic system can be researched in depth through the rational modeling and simulation, which provides a reference for design and manufacturing enterprises in the future excavators.