According to the structure of workbench and base of heavy hydrostatic bearing which is applied in heavy equipment, thermal deformation equations of the structure are deduced and boundary conditions for numerical simulation are established based on thermal elasticity theory. Then thermal deformation of hydrostatic bearing without load is calculated at different velocity. The results indicate that: temperature and velocity impacts a significant influence on thermal deformation of hydrostatic bearing. Thermal deformation increases as the velocity increases; workbench up-warps severely, oil-pad inclines towards outside to a certain extent, which results in the lubrication clearance emerges as wedge-shape deformation. The conclusions from thermal deformation calculation could provide theoretical basis for structure design of hydrostatic bearing and ravel out the thermal deformation problem.