In order to improve the machining accuracy of precision CNC lathe, and explore the fluid motion law in the closed hydrostatic guideway, three-dimensional model of hydrostatic oil chamber was established using preprocessor GAMBIT of FLUENT. The Finite Volume Method of Fluent has been used to the simulation of fluid three-dimensional velocity field and pressure field. The fluid velocity vector and pressure distribution graphs are obtained. They reveal the flow field law in the gap fluid. The simulation result of the pressure distribution shows that the flow pressure was not changing in linear gradient all around the gap under moving condition.