There are many reasons for the blackening of the glans penis, such as hyperpigmentation, excessive sex life, inflammatory stimulation and so on. 1. Hyperpigmentation: androgen secretion during male development is strong, so the penis can be engorged in the erectile state, resulting in the phenomenon of hyperpigmentation, resulting in the blackening of the glans penis, the phenomenon will be followed by an increase in the number of times of sexual intercourse and more and more obvious. 2. Excessive sexual life: long-term frequent sexual life, will lead to the penis for a long time in a state of congestion, blood flow in the blood vessels is not smooth silt in which can cause the blackening of the glans penis. 3. Inflammatory stimulation: glans inflammation will produce inflammatory reaction, inflammation long-term stimulation to the glans, can cause the phenomenon of black penis glans mouth. Causes of the blackening of the glans penis, if accompanied by uncomfortable symptoms, it is recommended that patients go to the hospital in a timely manner, in accordance with the doctor’s instructions to take standardized treatment.