This double-stage vacuum oil purifier is specially designed to treat transformer oil and other insulating oils from power plant, power station, electric power company, power transmission equipment, transformers, industrial and mining enterprises, especially suitable for on-site installation, maintenance and purifying high level new oil, or running oil from big power transmission and distribution equipment and transformers on national main power transformation grid, which is above 110-750kV. The machine effectively removes water content, impurities, gases etc from oil and highly improves its dielectric strength. With double stage vacuum, it has more powerful vacuum efficiency with more thorough dehydration and degasification.