The study aimed to investigate the sex differences in the reciprocal relations between parental corporal punishment and child internalizing problem behavior in China. Four hundred fifty-four Chinese elementary school-age children completed measures of their parental corporal punishment toward them and their own internalizing problem behavior at two time points, 6 months apart. Structural equation modeling revealed that both parental mild and severe corporal punishment significantly predicted child internalizing problem behavior for girls, but only parental severe corporal punishment marginally predicted child internalizing problem behavior for boys; child internalizing problem behavior predicted both mild and severe corporal punishment for boys but not for girls. The findings highlight the important role of severity of corporal punishment and child sex in understanding the relations between parental corporal punishment and child internalizing problem behavior and have implications for the intervention efforts aimed at reducing child internalizing symptoms or parental corporal punishment in China. (Contains 3 tables and 4 figures.)