VFD double-level high-efficiency vacuum oil purifier is mainly used for the vacuum purifiering treatment of costly oil, such as clean oil, imported oil, super-pressure transformer oil, inductor oil, etc, or for the injection of the vacuum oil into the transformer. Since double-level vacuum raises the vacuum degree of the whole system greatly, it can eliminate a large quantity of water and gas so as to avoid the harm done to oil quality owing to the repeated heating, and more effectively get rid of moisture, impurities, hydro-carbon gas and dissociate carbon as well as raise flash point and value of pressure resistance. If connected with regenerators, it can speed up to de-acid and de-color, further reduce the dielectric and acid value, as well as raise insulation. The clean oil with the breakdown voltage no less than 25kv can reach 60kv after one treatment of VFD double-level high-efficiency vacuum oil purifier and reaches more than 70kv after three-times purifiering treatment.