The length of a man’s penis is mainly related to race, heredity, age and developmental status, etc. Under the state of weakness, the penis length of normal adult males in China averages about 7.1cm, generally as long as the penis is not less than 4cm in the state of weakness is the normal length. China’s adult male penis length, in the soft state is generally between 3.5 ~ 12cm, an average of about 7.1cm. erection is generally between 7 ~ 18cm, an average of about 12.4cm. measurement of the length of the penis in the soft or erect state, the general use of a ruler on top of the pubic symphysis, will be the penis flat support, measured to the head of the penis urethral opening distance, that is, to arrive at the length of the penis. Under normal circumstances, the penis is smaller in the soft state, larger after erection, and the length increase is more obvious. As long as the penis can meet the sexual needs of the erect state can be normal. Therefore, as long as the penis is at a normal length and the sex life is satisfactory, men do not need to worry too much. Generally does not affect the normal sex life is not need to be treated.