Hydrocarbons in crude oil are mainly divided into alkanes, cycloalkanes and aromatics. According to the different composition of hydrocarbons, it can be divided into three types: paraffin-based oil, naphthenic base oil and intermediate base oil. Paraffin-based petroleum contains more alkanes; Cycloalkyl petroleum contains more naphthenes and aromatics; Intermediate base oil is between the two. At present, the crude oil that has been exploited in China is mainly low sulfur paraffin. Crude oil in Daqing and other places belongs to this category. Among them, the most representative Daqing crude oil has low sulfur content, high wax content and high freezing point, which can produce high-quality kerosene, diesel oil, solvent oil, lubricating oil and industrial paraffin. Shengli crude oil has high gum content (29%), high specific gravity (about 0.9 1) and high wax content (about 15-2 1%), which belongs to the sulfur-bearing intermediate group. Gasoline fraction has good lead sensitivity and is rich in naphthenes and aromatics, so it is a good reforming raw material.