Abstract: Compared with those from homogeneous marriages with lower parental education level,children from hypergamy marriages or homogeneous marriages with high-level education perform much better academically. Children from families of hypergamy marriage also tend to outperform those from hypogamy marriage families. There is also a diverging gap effect in educational assortative mating-the wider the marital educational gap,the better academic performance for the children from hypergamy marriage but the worse for the children from hypogamy marriage. Further more,the study finds that the level of parental unity plays a partial mediating role on the impact of marital education matching on children's academic performance. Among them,parent-child communication is the most effective way to activate family cultural capital. Parents from homogeneous marriage with high educational level are the ones who devote the most time in their children's upbringing and enjoy a closer parent-child relationship. However,in hypergamy,father and mother tend to form a complementary relationship in the division of parenting to improve the level of "co-parenting alliance" and the "new type of family cultural capital" can be activated more effectively to promote children academic performance. Even though educational assortative mating has become a "breeding ground" for inequality reproduction,a high level of "co-parenting alliance"may help slow down the transmission of intergenerational inequality.

Key words: educational assortative mating, children's academic performance, co-parenting alliance, activation of cultural capital, multi-category mediation analysis