Serum CA199, also known as glycoantigen 199, is a relatively specific tumor marker for the pancreas. It plays a very important role in clinical tumor screening or postoperative follow-up of pancreatic diseases. If the index of CA199 is higher than normal, tens or even hundreds of times, the possibility of pancreatic malignancy should be highly suspected, such as greater than 400 U/mL, and when combined with imaging tests, the clinical diagnosis of pancreatic cancer can be made when there is an occupying lesion in the pancreas. It is difficult to take pathological examination for pancreatic cancer, and surgery can be considered in early stage, but most of them have no chance of surgical treatment in middle and late stage, and the location of pancreas is deep, and it is difficult to pass puncture. So by virtue of imaging examination and tumor marker CA199, it is very important for clinical diagnosis of pancreatic cancer.