Abstract: To study the lubrication situations and the velocity conditions for obtaining the hydrodynamlc lubrication in the process of the hydrostatic extrusion, three lubrication situations were proposed in the process of the hydrostatic extrusion according to the lubrication theory of the plasticity process; A critical velocity formula for obtaining the hydrodynamic lubrication was put forward according to Reynolds equation. The results from the formula are in good agreement with the experimental data, and the crltlcal velocity formula may be used as a criterion of forming the hydrodynamic lubrication in the process of the hydrostatic extrusion.