Focused on the existing static pressure support cylinder which is determined to provide support force for the piston rod in the actuating cylinder of a whole hydraulic servo system, the problem has been considered of leaking oil by the actuating cylinder. The modal of the system was constructed with the Three Dimensional (3D) modeling software SOLIDWORKS, further more, the flow field was analyzed using ANSYS-FLUENT. Finally, the pressure distribution of system was gotten. In the end, the support force of the static pressure support is calculated.