Abstract: Informal institutions, like traditions, customs and habits, play an important role in the process of socioeconomic development. In some cases, informal institutions even shape the formal institutions. As China’s special marriage customs, uxorilocality, exchange marriage, children marriage and raising daughter-in-law marriage are all informal institutional arrangements. They could save transaction costs, shorten proxy chains, and maintain a marriage market equilibrium, which are all important parts of the institution of marriage in China.