The series are mainly used to filter different insulation oil. The series adopt two-stage pump to improve the degree of vacuum furthest so that they can efficiently eliminate the water, gas (C2H2) in the insulation oil. The filtering system which contains three-stage filtering devices can eliminate various impurities. At the same time, the regeneration purification system can eliminate the oil sludge, free carbon and other deleterious materials which affect the working order of transformer so that the acid value and the cost of insulation oil are recovered.