Taking the rotary vane hydraulic steering gear system as a research object, the hydraulic system model of rotary vane hydraulic steering gear and the hydrodynamic model of rudder blade are established respectively based on the cosimulation strategy of AMESim software and Simulink software. The simulation results show that the output rudder angle of cosimulation model can better track the change of given rudder angle and satisfy the fastness and accuracy required, and the switch action of the servo valve would cause pulsations and shocks on the flow and pressure of rotary vane hydraulic cylinder.