The function of the turbine oil of the 700MW hydrogenerator unit of the China Three Gorges Power Plant and the reasons for the deterioration of the oil quality during the operation process were introduced,the characteristics of the turbine oil system of the unit and the problems in the initial stage of operation were analyzed.In order to solve the problem of the unit in the lubrication process,a strategy for separating the hydraulic oil and the bearing oil in the oil depot was proposed.After comprehensively analyzing various processes,the treatment process suitable for the oil of the unit was selected.The practice shows that the oil electrostatic filtration technology can well reduce the pollution degree of the oil.