Dark-field microscopic examination method: It is the main method of syphilis pathogenesis diagnosis in China at present. It is suitable for the detection of stage I syphilis and early stage II syphilis. The site of the test is mainly the hard chancre, but can also be taken from the cervix, vagina, lymph nodes and other places. A positive test can confirm the diagnosis, while a negative test cannot exclude the diagnosis of syphilis. Silver plating staining method: The clinical significance is basically the same as that of the dark field examination method. Using syphilis spirochetes are silver-friendly and can be stained brown-black by silver solution, and then observed by ordinary high-powered microscopy. Direct immunofluorescence method (DFA): It is a method used more often abroad, and its specificity and sensitivity are better than the dark field examination method. The specific anti-syphilis spirochete monoclonal antibody is labeled with fluorescein, and if syphilis spirochetes are present in the specimen, the spirochetes can be seen under the fluorescence microscope by specific binding of antigen and antibody, and the spirochetes can be seen in apple green color.