<p>This study examined the causal effect of women’s education on both the extensive and intensive margins of fertility in China, by exploiting provincial and temporal variation in the implementation of the 1986 Compulsory Education Law. Using seven waves of the China Family Panel Studies (2010–2022) and restricting the analysis to women aged 35–50, the study covered 30,852 observations. The results show that additional schooling significantly reduces the probability of having any children, lowers the number of children among mothers, and decreases the likelihood of a second birth, with no consistent evidence of an effect on third births. The largest reduction occurs at the second-birth stage. Mechanism analyses reveal that education discourages both first and second births by lowering the perceived importance of family life, whereas further discouraging second births through weakened functional fertility motivations, delayed marriage, and higher educational expenditures for the first child. Moreover, income gains from education exhibit a nonlinear relationship with fertility, with an inverse U-shape for first births and a U-shape for second births. These findings highlight the importance of distinguishing between extensive and intensive fertility margins in understanding how education shapes fertility decline.</p>