The structure of the oil cushion has an important influence on the workbench rigidity, pointed to this problem, used the fan cushion for an example, changing the depth, shape and structure of the oil chamber of three aspects, its statics and the flow field are analyzed. Based on fluidstructure coupling analysis ANSYS Workbench，comparative analysis was carried out of the trough, fanshaped, and round of three oil chamber shape, the flow field generated pressutre was applied to the oil chamber of oil cushion. Mechanical analysis is done on the oil pad, which provides the evidence to the optimization design of cushion structure.