Controlling impurities in oil has been a problem in application of health science and medicine. After cold pressing, impurity removal and refining, there are still some impurities, such as free fatty acid, fat-soluble pigments, saponin, heavy metal and microorganism in camellia oil, and these impurities can be totally eliminated if every step in preparation of camellia oil has been strictly controlled. The separation and quality control of oil was expatiated by comparing all indexes of edible oil with that of medical oil, and the relative researches in oil used for injection was also discussed.