The design principle and the compensation procedure of the oil film thickness feedback compensation device for large machine tool hydrostatic guideway were described in detail. The oil film thickness was measured by grating ruler, and the mathematical model of oil film thickness and flow rate was used to calculate the difference of oil quantity and output corresponding electrical signal by PLC program, the amount of oil required for the recovery of the oil film thickness was calculated, the frequency of the motor was adjusted,then the speed and fuel supply were adjusted. Practice has proved that this scheme is feasible.