It is a painless inflammatory reaction caused by the invasion of syphilis spirochetes into the mucous membrane of the skin. It usually occurs in the external genitalia, mainly in the coronal groove, glans, prepuce and tether in men; in women, it is seen in the labia majora and minora, labial tether, perineum and cervix. The typical chancre starts as a small erythematous patch, which rapidly develops into a painless papule, and the papule forms a hard node within a few days. The hard chancre of syphilis belongs to stage I syphilis, which is particularly contagious. The untreated hard chancre can last for 3-4 weeks and will subside after 1-2 weeks of treatment. After the diagnosis of syphilis, the drug of choice is penicillin. The concentration of penicillin in the blood must be stable for more than 10 days to completely clear the body of the syphilis spirochete. The commonly used clinical drug is benzathine penicillin, commonly known as long-acting penicillin, which is injected once a week with 2.4 million units each time for 2-4 times.