The average adult male penis is 5-6 cm in length when soft and twice as long when erect as it is when weak. If the penis is less than 4 cm in length when weak and less than 8 cm in length when erect, then it is called short penis. The reasons for the formation of short penis are various, there are congenital factors, there are also acquired factors, the influence of genetic genes is the most fundamental, common causes are as follows: 1, genetic factors penis and other organs of the body, its size and morphological characteristics to be controlled and influenced by genetic genes. 2, development and nutritional status Generally speaking, adult men are physically fit, tall, their external genitalia, including the penis, scrotum development is also better, the penis may be thicker; conversely, it may be relatively small. However, it must be reminded that the size of the penis is not proportional to the height. 3, obese Especially some pubic symphysis, perineum fat plump prominent men, often the development of the penis is poor, compared to the normal male penis will be relatively short, and the patients themselves visualize their penis difficulties, more think their penis is small. Indeed, compared with the fat body on the short side of the penis in marriage may bring some difficulties and undesirable sexual life. 4, other Suffering from orchitis, cryptorchidism, testicular hypoplasia and other diseases and endocrine imbalance, androgen deficiency, may cause penis short. At present, men have several misconceptions about the problems related to penis shortening in general, the most important of which is that there are many people who believe that the length of the penis under the norm is very important. In fact, the length of the penis under normality is not very relevant for the assessment of sexual function and cannot be used as the main indicator to evaluate the function of the penis. Therefore, it is not the case that the longer the penis under normality is the better. Generally speaking, Chinese men in a normal state, the length of the penis is abnormal if it is less than 4cm and less than 8cm when erect, which will have an impact on sexual life, but the assessment of penis size needs to be done by a specialist, and some people are reading some unhealthy books or pornographic videos and websites, and are misguided, blindly seeking “long “This kind of psychology is not desirable.