The operating condition of hydraulic excavator is complex.To some degree,inadequate working conditions and external factors have a great impact on the security of its core controlling system and the working stability of the hydraulic excavator.Targeted on the electric-hydraulic servo system of hydraulic excavator,the hydraulic servo mathematical model and the AMESim simulation model was established,and the pressure and flow characteristics were analyzed through simulation.In addition,it provided important theoretical basis and references value for the improvement of the electric-hydraulic excavator as well as the application for the construction machinery,through the judgement of the system working stability based on the systematic Bode picture and Nichols picture.