Abstract: Deactivation analysis and regeneration performance investigation were carried out on the catalyst which appeared obvious deactivation in the first catalyst bed of the reactor in a vacuum gas oil hydrofining unit of a refinery. The fresh catalyst,deactivated catalyst after toluene extraction and the regenerated catalyst were detected by means of X-ray fluorescence spectrometer (XRF)，specific surface area and aperture analyzer，and X-ray photoelectron spectroscopy (XPS) . The results showed that the specific surface area and pore volume of the deactivated catalyst decreased obviously ，and the pore volume of regenerated catalyst was obviously recovered, but the specific surface area was not recovered completely. The main reason for the deactivation of the catalyst was that the inorganic materials containing P, Fe and Si elements were deposited on the surface of the catalyst, which blocked or deposited in the catalyst channel. Compared with the fresh catalyst，the deactivated catalyst had no catalytic activity，and the regenerated catalyst showed some initial activity，but the activity dropped sharply，so the deactivated catalyst was permanently deactivated.

Key words: vacuum gas oil, hydrofining catalyst, deactivation analysis, regeneration performance