Abstract: The problems in lubricating oil clay purification device were analyzed and the corresponding retrofit techniques were proposed and applied, including: adjusting feed oil flow, adding material degassing tower, adopting complexing denitrification process, solving the corrosion of the overhead vacuum evaporation system. The technical improvement in equipment include: replacing plate and frame filter press and clay feeder, retrofitting pump at the degassing tower bottom, solving the scaling problems of water ring vacuum pump. Some techniques based on the current situation were put forward. A good social and economic benefits are obtained followed the above retrofit measures.