This study investigated the developmental cascades of marital quality, harsh discipline, and child externalizing behavior in a Chinese sample of 976 father-mother dyads and their children (initial Mage = 7.63 years, 52.2% boys). Marital quality, harsh discipline, and child externalizing behavior were assessed at three annual measurement occasions. Cascade models indicated the unidirectional rather than bidirectional relations between the variables over and above within-time covariance and across-time stability. Both increased maternal and paternal marital quality in a given year predicted decreases in child externalizing behavior in the next year. Child externalizing behavior in a given year predicted increases in both maternal and paternal harsh discipline in the next year. Moreover, increased paternal but not maternal marital quality in a given year predicted decreases in psychological aggression rather than corporal punishment in the next year. Moreover, the indirect effect of marital quality on child externalizing behavior through harsh discipline was not found. In addition, the potential indirect effect of marital quality on harsh discipline through child externalizing behavior was observed. These findings highlight the importance of examining developmental cascades across family subsystems and efforts to improve marital relationship to promote child adjustment as well as parent-child interaction during middle childhood in Chinese society.