To improve both the static and the dynamic performances of the aerostatic journal bearing,the flow characteristics in the bearing clearance,the displacement impedance,as well as the load carrying capacity were analyzed and optimized.The flow structures in the bearing clearance were analyzed by numerical simulation method.The supersonic region in the flow field of the air film was eliminated to suppress the micro-vibration.The stiffness and damping of the bearing air film were calculated,and the displacement impedance was further achieved based on the Engineering Simplification Algorithm-Computational Fluid Dynamics method.The influences of bearing parameters on the displacement impedance were discussed.It is found that the pressure in the air film decreases from the orifice to the outlet of the air film,and the formation of the shock waves at the outlet of the orifice can induce the vortex flow and then cause the occurrence of the micro-vibration.The formation mechanism of the micro-vibration is similar with that of the thrust bearing.The mathematic model for optimization was established,the displacement impedance and the load carrying capacity were both considered as design objectives,and the elimination of the micro-vibration was also considered.Several cases with different eccentricity ratio and excitation frequency were discussed.Through optimization,the mechanical performances of the journal bearing are improved,and the optimization and analysis process can provide a reference for engineering application of design of the aerostatic journal bearing.