A penis that can be erect but usually shrinks in the pubic hair may be normal, or it may be caused by a hidden penis. Usually when the penis is sexually aroused, or after being stimulated, the arterial blood vessels of the penis dilate, at which time the blood will enter the cavernous body of the penis, resulting in an erection, hardening and lengthening of the penis. But penile erection after ejaculation or not stimulated, the penis spongy body will be reduced, at this time the penis will be weak, so it will be manifested as the usual penile shrinkage in the pubic hair inside, this is a normal physiological performance. If the patient is too obese or prepubic fat accumulation, penile circumcision scar formation, postoperative scrotal edema, may lead to cryptorchid penis, this time the patient will also be manifested as the penis can be erect but usually shrink in the pubic hair. In addition to this, children with abnormal penile anatomy and abnormal development of the penile meatus may develop cryptorchid penis, and the patient may show symptoms of a penis that can be erect but is usually retracted in the pubic hair. It is recommended that the organism needs to consult a doctor in time when the penis can be erect but usually shrinks in the pubic hair, and if it is a normal physiological phenomenon, it can be left untreated. If it is caused by disease, you need to follow the doctor’s advice to choose the appropriate measures for treatment.