According to the national standard, edible oil is divided into four grades according to the degree of "refining", namely, grade one, grade two, grade three and grade four. Among them, four levels are rare, and the market is dominated by one, two and three levels.

The primary and secondary oils are highly refined, degummed, deacidified, decolorized and deodorized. The color is clear and tasteless, beautiful, and it is not easy to become solid at low temperature. Less impurities, high smoke point and less oil smoke when cooking.

The refining degree of tertiary and quaternary oils is low, and usually only degumming and deacidification are carried out. The refined oil is dark in color and has obvious raw material flavor. For example, soybean oil has a beany smell. The original nutrients such as carotene and vitamins are completely preserved.

The grade of edible oil is divided according to its variety, quality and processing technology. Edible vegetable oils in China's market are divided into one, two, three and four grades, such as soybean oil, rapeseed oil, cottonseed oil, rice bran oil, sunflower oil, corn oil, leached peanut oil and leached tea seed oil.

However, pressed peanut oil, pressed tea seed oil and sesame oil are only divided into grade one and grade two. Product quality grade is the basis for evaluating the quality of vegetable oil, that is to say, different grades have different quality limits, including color, smell, transparency, acid value, smoke point and other indicators. The higher the grade, the stricter the limit.