The phenomenon of blood vessels protruding from the penis during erection may be a normal physiological phenomenon, or it may be a symptom of some diseases such as varicose veins of the penis. 1. Physiological phenomenon: Normal men will experience sympathetic nerve excitation, blood vessel expansion, penile corpus cavernosum congestion, and a large amount of blood into the penis, thus leading to the protrusion of blood vessels in the penis, which is a normal physiological phenomenon and will not cause harm to the human body, and does not require medication and other treatments. When the erection is over, the blood vessels will gradually return to the normal state. 2. Pathological phenomenon: venous thrombosis of the penis, poor blood flow in the penis and other factors can lead to abnormal expansion of the venous plexus in the penis, tortuous, thus showing the symptoms of penile blood vessels protruding during erection. In this case, you need to go to the hospital, after the cause of the disease is clarified to carry out targeted treatment. If the blood vessels are protruding from the penis during erection, you should consult a doctor in time and take active treatment.