Confirmation of Phase I syphilis requires a comprehensive diagnosis combined with medical history, clinical manifestations and laboratory tests to make a careful diagnosis. The incubation period is usually 2~3 weeks. (1) Hard chancre is 1~2cm in diameter, round or oval, slightly higher than the skin surface, with mild vesicles or shallow ulcers, little discharge, flesh red or dark red, no pain, no itch, cartilage-like hardness when diagnosed. It is usually solitary or can be multiple. (2) The inguinal lymph nodes or lymph nodes near the affected area may be enlarged, often several, varying in size, hard, non-adhesive, non-ruptured, and painless. (3) May subside on its own. Laboratory tests: (1) microscopic examination: syphilis spirochetes can be found in the tissue fluid of skin lesions or lymph node puncture fluid; (2) positive serological test for syphilis. The specific syphilis spirochete antigen serological test (FTA-ABS and TPHA) starts to appear positive 1-2 weeks after the onset of the chancre, and the non-spirochete antigen test (RPR) starts to appear positive 3-4 weeks after the onset of the chancre. Therefore, if there is clinical suspicion of syphilis and the serum reaction is positive, it should be reviewed after 1 to 2 weeks. If the rash has been present for 1 to 2 months but the serologic reaction is still negative, then sclerosing chancre can be excluded.