To improve the machining accuracy of Nanosys-1000 ultra-precision machine for aspheric optics, the flow distribution of a hydrostatic thrust bearing which is one of core components in the machine was researched to reveal the characteristics of the bearing．A simulation model of fan-shaped oil pad for a symmetrical structure hydrostatic thrust bearing was created by using ANSYS/Fluent software, and the flow field distribution law and bearing characteristics of the oil pad on a inlet oil pressure of 1.3-1.9 MPa and an oil film thickness of 20-36 μm were analyzed by using a laminar flow model. The results show that the pressure in the oil chamber region is very uniform and it decreases linearly along resistive oil edges. Furthermore, the oil film bearing capacity is linear growth with the oil cavity pressure.Under the same inlet oil pressure, the smaller the oil film thickness is, the greater the oil film bearing capacity is; when inlet oil pressure is 1.5 MPa, the oil film thickness decreases from 36 μm to 20 μm and the oil cavity pressure increases from 3.05×105 Pa to 8.02×105 Pa; accordingly, the oil film bearing capacity increases from 880 N to 2 109 N. Under the same load, the higher the inlet oil pressure is, the larger the oil film thickness is; when the oil film bearing capacity is 1 320 N, the inlet oil pressure increases from 1.3 MPa to 1.9 MPa; accordingly, the oil film thickness increases from 26 μm to 30 μm. Moreover, under the same oil film thickness, the higher the inlet oil pressureis, the larger the oil flow is; when the oil film thickness is 28 μm, the inlet oil pressure increases from 1.3 MPa to 1.9 MPa; accordingly, the oil flow increases from 0.179 L/min to 0.231 L/min. The relative research results have been verified in the hydrostatic thrust bearing of the Nanosys-1 000 ultra-precision machining tool.