An erection that is fast and soft may be due to a lack of sustained sexual stimulation, psycho-psychological factors and cavernous arteriovenous fistula of the penis and other conditions, it is recommended to go to the hospital for further examination. 1. Physiological factors: If there is no sustained sexual stimulation after erection, or if there is not enough pleasure from sexual stimulation, it may lead to decreased arousal or difficulty in inducing effective nerve excitation to maintain erection. 2. Mental and psychological factors: if due to work pressure or emotional reasons such as mental lack of concentration, lack of excitement and other conditions, or excessive sympathetic nervous tension, anxiety, resulting in the constriction of the blood supply arteries of the penis, the blood supply is reduced, and other conditions may lead to faster weakness. 3. Cavernous arteriovenous fistula: If there is a cavernous arteriovenous fistula of the penis, the cavernous arteries of the penis are engorged with blood quickly through the arteriovenous fistula back, resulting in insufficient blood supply to the penis, it is difficult to maintain a long time to get an erection. Therefore, the erection of the fast soft also very fast, it is recommended that the patient timely to the hospital for further examination, clear cause of the disease in the doctor’s guidance under the treatment.