Abstract: To find out the effects of geometry of the oil seal edge on flow field and load capacity of NC machine's hydrostatic oil cavity,computational fluid dynamics (CFD) simulation is applied.Results indicate that the height,length,angle and microstructure of the oil seal edge have important effects on the vortices of flow field and load capacity.By changing these factors,the pressure of the flow field and the load capacity can be improved.The results can be used to optimize the design of geometry of hydrostatic oil cavity and improve its performance.