The proportional directional valve and direct drive electro-hydraulic servo valve have the advantages of quick response, strong stain resistance and so on, and are widely used in various industrial fields. According to the structure and working principle of the proportional direction valve and direct drive servo valve, AMESim software was used to set up simulation models of the two kinds of valve.The flow characteristic curves of the two kinds of valve under common faults were simulated. The simulation data were compared with the experimental data from the electro-hydraulic servo valve performance testing platform, the accuracy of the simulation model was verified.The analysis to these two kinds of valves can provide reference for the selection of servo valve in the design of hydraulic system under different working conditions and the fault maintenance.