In this paper, the development process of XD® series adsorbent is briefly introduced, the distinction is characterized between different adsorbent; explored the use of adsorbent and sorption properties; found the relationship between its physical-chemical properties and its regenerative properties in electric oil; expound the superior performance on transformer oil regeneration; finally introduce XD® series of adsorbent to deal with the practical application on large transformer practically. By the component analysis of transformer oil before and after the oil treatment, As well as the nine-year running of a EHV transformer, prove the reliability of the technology of raising the transformer insulation lever by oil treatment.