According to the research, it is now believed that the substances such as benzo(a)pyrene, aflatoxin and nitrosamine produced in some foods have definite carcinogenic effects. 1. Benzo(a)pyrene: after absorbed by human body, it can combine with DNA, cause mutation of DNA, and cause cell cancer. Benzo(a)pyrene is commonly found in high-temperature fried foods such as doughnuts, smoked foods such as grilled fish and bacon. It can lead to esophageal cancer, stomach cancer, lung cancer and so on. 2. Aflatoxin: It has the closest correlation with liver cancer. It is commonly found in moldy coarse grains and their products such as peanuts, corn, rice, beans and poor quality peanut oil, soybean oil and other foods. 3. Nitrosamine: it has certain correlation with the occurrence of esophageal cancer and other cancers. It is commonly found in cured foods such as bacon, smoked fish, salted fish, sauerkraut and kimchi. There are other carcinogens in food such as acrylamide, etc. In our daily life, we should try to choose fresh and less processed food cooked at low temperature in order to avoid the harm of carcinogens to our body to the maximum extent.