The chancre of syphilis can be detected by observation, provided that the characteristics of the chancre of syphilis are known. 1. The chancre is the main symptom of stage 1 syphilis and often appears 2-4 weeks after the occurrence of unclean sexual intercourse. 2. In men, the chancre can be found on the foreskin of the penis, the coronal groove, the ligament and the glans. In women, it is most common on the labia majora and minora, the ligament, the urethra, the perineum or the cervix. 3. A typical chancre is round, 1 to 2 cm in diameter, with clear boundaries, and the sores are slightly elevated above the surface of the skin, appearing as flesh-red vesicles with a small amount of exudate on them. The chancre is cartilaginous when palpated, while in women the chancre has no pain or tenderness, the number of lesions is usually only one, and the surface of the lesions is clean. If any of the above characteristics are found, the patient should go to the hospital and receive systematic diagnosis and treatment.