In the past century, China has undergone rapid and dramatic social and economic changes. This article describes trends in educational assortative marriages of cohorts born in 1906-1995 in China. We measure educational attainment relatively as an individual's percentile position in the education distribution of a 10-year birth cohort and study trends using comparable, easy-to-interpret couple rank-rank correlations. We analyze microdata samples from the 1982, 1990, 2000, and 2010 China censuses and the 2015 1% intercensus survey and nationally representative surveys between 1996 and 2018. We find a large and steady increase in educational assortative marriage over the past century, except among those born in 1946-1965, whose schooling and marriage were impacted by the Cultural Revolution. Our study highlights the critical roles of social, political, and economic contexts in shaping trends in educational assortative marriage.