Penis erection for a period of time and then soft is erectile dysfunction, consider psychological factors elements, organic lesions such as the penis itself disease, vascular disease, neurological diseases, surgery and trauma, endocrine diseases and so on. 1. Psychological factors Commonly, such as husband and wife’s daily relationship is not coordinated, inappropriate or insufficient sexual stimulation, adverse sexual experiences, anxiety and depression may lead to penile erection for a period of time and then soft. 2. Organic lesions (1) Penile disease: if the patient has circumcision, penile deformity, may cause the penis erection for a period of time and then soft. (2) Vascular disease: if the patient has atherosclerosis, arterial stenosis, arterial injury and other vascular diseases, may cause the penis erection for a period of time and then soft. (3) Neurological diseases: If the patient has stroke, Parkinson’s disease, lumbar disc disease and other neurological diseases, it can also lead to penile erection for a period of time and then soft. (4) Surgery and trauma: blood vessel and nerve injuries related to penile erection, such as surgery on large blood vessels and pelvic fracture, can also cause penile erection to become soft after a period of time. (5) endocrine disease: patients with hypogonadism, thyroid disease, can also cause penile erection for a period of time and then soft. It is recommended to go to the hospital in time to see a doctor to find out the cause of the disease and take symptomatic treatment to avoid delaying the condition.