Malignant tumors are very common clinically, and routine blood tests cannot reflect the malignancy degree of malignant tumors. In early stage of tumor, there is no obvious change in blood routine. In the middle and late stages of tumor combined with infection, the white blood cells may increase in the routine blood test; in cachexia patients, the red blood cells and hematocrit will decrease and anemia will appear, so the routine blood test of malignant tumor patients does not reflect the degree of malignancy. Clinically, malignant tumors can be examined and identified by tumor markers, such as tumor markers for liver cancer patients are methemoglobin, if methemoglobin is high, it is an important basis for clinical diagnosis of liver cancer; for colorectal cancer patients, carcinoembryonic antigen, CA199, CA724, these tumor markers can reflect the progression of colorectal cancer; for breast cancer patients, blood tumor markers such as CA125, CA153, CEA, etc. can help to make diagnosis or differentiation.