A detailed analysis and mathematical modeling of armature assembly of doublestage dualnozzleflapper electrohydraulic servo valve were given. On basis of this, the process of submodel modeling and parameter setting of armature assembly selfdefined with AMESet software were expatiated. A complete servo valve model of the nozzle flapper was built. It is proven by the graph gotten in the simulation run, the effectiveness of the model of armature assembly and the complete servo valve model of the nozzle flapper.