Under normal circumstances, the size of the penis varies greatly among different races and different individuals. According to a survey, the average length of the penis of adult Chinese Han men is about 7 centimeters in normal conditions and about 13 centimeters when erect. In general, the penis can reach 5 or 6 centimeters when erect, and can also meet the normal urinary and reproductive functions. However, it is currently considered ideal to have a penis that is 13 centimeters or more in length when erect. Penis shortening can be caused by a number of congenital, acquired and other various reasons, as well as obesity, trauma and so on. Penis lengthening is generally seen in two cases, one is the penis is too short to meet the standing urination and reproductive function; the second is the length of the penis is basically normal, but to a certain extent can not meet the sexual requirements of the female party, in order to improve the quality of sexual life and surgery. Penis lengthening surgery has been improved and has become a safe and less invasive surgery, which can usually lengthen 3-4 centimeters.