A circle of purple color in the coronal groove of the glans is mostly caused by the deepening of color due to less local blood circulation in the glans. Common factors include excessive and frequent masturbation, or having a long foreskin or narrow foreskin opening, which leads to local blood circulation disorders, resulting in ischemia and hypoxia in the tissue at the front part of the glans, creating a purple-colored appearance. Patients can check the color Doppler of the penis or cavernous body imaging to determine whether there are abnormalities in blood vessels and blood supply. Also in the cold environment, it can lead to a decrease in local blood supply and a purplish appearance of the skin mucosa. This condition has no obvious symptoms of discomfort and does not require special treatment. Only when abnormal function of the blood vessels of the penis is detected, such as arteriovenous fistula or narrowing of the lumen, does special treatment become necessary.