“No harsh demand for good from father to son” is an important ethical proposition. Mencius believes that the phenomenon of “a gentleman does not teach his son by himself” is externally due to the forbiddance of some behavior based on the circumstances of the specific relationship between father and son. On the ethical basis，it is due to the affection of the blood relationship，and these claims are closely related to the theory of original goodness of human nature. There is a certain limit to “no harsh demand for good” in Mencius，not for all the fathers and sons in the world，but could be only for the “unscrupulous child” and the action-oriented concept of “doing” within Xia，Shang，and Zhou Dynastiesspecifically. Mencius specifically distinguish the differences of the relationship between father and son from the relationship between friends as well as the relationship between father and son from the relationship between Master and apprentice，and distinguish the relationship of serving relatives from serving monarchs. Mencius believes that each aspect has its own rules which cannot be changed. The so-called “exchange one’s son and teach someone else’s son” is not “no admonishing nor teaching”，which not necessarily leads to “alienating your son”. The moral concept of that Father and son have affections as well as bold relationships still plays an important role. In “Mencius”，in addition to the text’s surface meanings，there should also be implicit meanings between the lines.Mencius not only emphasizes that the father should “discipline” his son，but also emphasizes more on “raising children” by “fostering and irrigating”. He did not advocate “no teaching”，but supported “teaching by precept and example”，and also did not advocate “exchanging one’s son and teaching someone else’s son”. In case of a son with a contrary character，he should still do the teaching himself. This is also a reflection of the thought of Mencius on “norm” and “right” in the process of fathers and sons getting along with each other.