Insulin was first discovered by Canadian F.G. Wanjin and C.H. Best in 192 1 year. 1922 began to be used in clinic, saving the diabetic patients who died in the past. Until the early 1980s, almost all insulin used in clinic was extracted from the pancreas of pigs and cows. The insulin composition of different animals is different, and the insulin structure of pigs and humans is the most similar, only one amino acid at the carboxyl end of B chain is different. In the early 1980s, human insulin was successfully produced from microorganisms by genetic engineering technology, and it has been applied in clinic.