Abstract: In the context of the universal two-child policy,it is of great significance to pay attention to the family environment,social adaptation and its associations of the one-child family and the two-child family,which could help improve the family environment and promote the growing of children in different types of families.Cluster sampling was used to investigate 2,523 one-child families and 3,099 two-child families in 6 cities,and the results showed that:(1) the family adaptability and positive parenting in the one-child family were significantly higher,and the social adaptation of children in the one-child family was significantly lower; (2) positive parenting played a mediating role between family environment and social adaptation of children; (3) the mediating effect of positive parenting in the one-child family was significantly higher than that in the two-child family,that is,children in the one-child family are more likely to be affected by the mediating effect of positive parenting.

Key words: family environment, positive parenting, social adaptation, the universal two-child policy