The invention discloses a hydrostatic bearing and a hydrostatic guide rail 
assembly. The hydrostatic bearing comprises a supporting block, a cover plate, a bearing 
piston, a bearing disc, an elastic element and a throttler, wherein an auxiliary cavity is formed in the upper portion of the supporting block, a main cavity is formed in the lower portion of the supporting block, and the auxiliary cavity communicates with the main cavity; the cover plate covers the supporting block and is provided with an 
open hole communicating with the auxiliary cavity; the bearing 
piston is contained in the auxiliary cavity; the bearing disc is connected with the top of the bearing 
piston extending out of the 
open hole and used for bearing external loads; the elastic element is arranged in the auxiliary cavity, one end of the elastic element abuts against the bearing piston, and the other end of the elastic element abuts against the bottom face of the cover plate; and the throttler is installed in the supporting block, an outlet of the throttler communicates with a first channel through a second channel, and an inlet of the throttler communicates with external 
oil supply equipment. According to the hydrostatic bearing and the hydrostatic guide rail 
assembly, 
small hole throttling is combined with a piston type displacement self-compensation structure, so that when the bearing force borne by the hydrostatic bearing changes, 
rapid response can be achieved, the hydrostatic bearing can return to the original position within a short time, and then quasi-infinite rigidity is achieved.