As we all know, STD has its own specificity and accurate diagnosis is important. What principles should we follow in order to avoid missing or misdiagnosis? I think it is enough to pay attention to three elements: First, the epidemiological history, that is, asking the patient whether he has a history of unclean sexual intercourse or similar behavior, and the related situation of sexual partners. Second is the clinical manifestations, typical symptoms and signs are important clues and basis for the diagnosis of certain diseases. Third, laboratory tests, test results can provide strong evidence for a correct diagnosis, and some are the gold standard, such as the diagnosis of gonorrhea when gonococci are cultured in the patient’s urethra. The combination of the three elements can be analyzed to make a correct diagnosis.