Abstract:The model of a load simulator system is established,and aimed at extraneous force existed in it is simulated with analysis.For the nonlinear characteristics of hydraulic servo system existed,so power bond graph modeling theory was applied,so as to display its advantages on nonlinearity.By comparing test and simulation results,the extraneous force bond graph model accuracy was verified.Simulation and experiments show that the extraneous force generated by the passive uncompensated loading force is huge in amount,which seriously affecting the loading accuracy of loading system.The study result provides a theoretical basis for extraneous force simulation study of the load simulator.