Abstract: Lubricating base oils with high viscosity index are the important basic raw materials for production of high-grade internal combustion engine oil. At present a few domestic manufacturers produce them with low output, and No domestic plant produces the ultra-high viscosity index base oils. The preparation of ultra-high viscosity index lube base oils was studied. The results indicate that when oily wax is used as feed, the lube base oils with viscosity index higher than 146, which meet the requirements of UVHVI150, UHVIS150 and UHVIW150, can be produced by combined technology of iso-hydrodewaxing and ketone-benzol dewaxing process.