Black spots on men’s genital organs may be normal phenomenon, or it may be caused by pigmentation, stimulation of external forces, or other diseases. 1. Normal phenomenon: with age, about the age of 12 years old in men, there will be the development of secondary sexual characteristics, the local color may be darker, consider and the role of androgen secretion. 2. Pigmentation: Excessive foreskin scale caused by long foreskin and prepuce will affect the local metabolism and lead to pigmentation. 3. External force: the formation of damage by external force, after treatment of local pigmentation, resulting in black spots on the skin; often wear chemical fiber underwear, and local friction stimulation, resulting in pigmentation; before and after sex, do not pay attention to hygiene, frequent sex, excessive masturbation, which can lead to the local growth of black spots. 4. Other diseases: when black spots appear on genital organs, one should also go to the dermatology department of hospital for examination to know whether it is related to pigmented nevus, mucous membrane nevus (freckle-like nevus), melanoma and other diseases. Black spots on men’s genital organs, which grow faster in a short time, need to go to the hospital in time. If they are caused by pathological factors, it is recommended to combine with the doctor’s advice to treat them as early as possible.