Abstract: The floccules in 120BS bright stock produced in SINOPEC Jingmen Company occurred during storage in an environment below 5 ℃. To solve this problem, the analysis of floccules structure and dewaxing test of the hydrotreated bright stock were made in lab and industrial trial practice was conducted. The results indicate that the floccules consist of high solidification point hydrocarbons, like long chain paraffin, less branched alkanes and long side chain naphthene and that the good and stable qualified feed for acetone-benzol dewaxing can be obtained by optimization of crude oil composition, operation conditions of propane deasphalting, furfural extraction and hydrotreating, and the 120BS bright oil without the floccules can then be produced by carefully controlling the operation conditions of each step in acetone-benzol dewaxing process. The 120BS complies with the standard of API II and SINOPEC.