Abstract: People gave birth to their children, but did not nurture them. This custom was quite prevalent in the two Song Dynasties. It is rarely seen in Chinese history that it had existed for so long and covered a quite large area. It was mainly because of peasants’ poverty, collection of poll tax, restriction of inheritance of property, prevalence of marrying daughters at high cost, and disasters. Such custom restricted the growth of labor force in some regions and brought about the disproportionality between male and female. At the same time, it caused more criminal cases and corrupted social morals.