In recent years, the incidence of malignant tumors is increasing, and people are afraid of talking about “cancer”. Therefore, we all hope to check tumor markers during medical checkups for early screening, diagnosis or exclusion of malignant tumors. However, after checking tumor markers, some people are happy because of the normal results and soon they are diagnosed with tumor by doctors; others are sad because of the abnormal results and cannot exclude tumor even after a long time. Why would such a situation occur? Tumor markers are a kind of biochemical substances used to reflect the existence of malignant tumors. Ideally, once it increases, the diagnosis of malignant tumor should be confirmed. However, in reality, there is no tumor marker that can fully meet this definition. In other words, an increased tumor marker does not necessarily indicate the presence of malignant tumor, while a non-increased tumor marker does not necessarily indicate the absence of malignant tumor. In fact, in addition to the occurrence of malignant tumor, inflammation and infection in other organs, such as stomach, intestine, liver and gallbladder, genitourinary system, lung, etc., can lead to low level increase of some tumor markers, i.e. “false positive” performance. However, it is important to note that persistent and large increases in tumor markers should alert the development of cancer. In addition, the quality of hospital specimens, operational factors, reagent types and methodological issues will also affect the accuracy of tumor marker measurement results. Therefore, if a medical examiner encounters an elevated tumor marker, he or she can visit an oncology hospital. The doctor will first make a comprehensive analysis of the normal value range, the magnitude of the increase, personal symptoms and the characteristics of this tumor marker. Generally speaking, for low level increase of tumor markers which are slightly higher than the upper limit of normal value but without obvious suspicious symptoms, or with very low specificity, they can be rechecked once a month in the oncology hospital after proper conditioning and rest. If they continue to fluctuate in the original value range or have a tendency to increase, they should be rechecked in both oncology hospital and other hospitals for the same item. If it continues to increase, the doctor will check carefully and if necessary, CT, PET/CT and other examinations will be needed. If the tumor markers fluctuate up and down repeatedly, but there is no overall trend of continued increase, at this time, patients do not need to be overly nervous. In conclusion, it is clinically proven that some tumor markers can screen and diagnose the corresponding tumors at an early stage. For this reason, it is recommended that those who are engaged in high pollution work and enter into high risk age should be examined once a year, and those who have family history of tumor should cross into the ranks of medical examination in advance.