This study investigated the influence of parents’ marital quality on elementary school students’ homework efforts, and the mediating effect of parent-child cohesion in the relationship between parents’ marital quality and students’ homework efforts. A ninemonth longitudinal tracking investigation was adopted for this study. Six hundred and twenty-five elementary school students and their parents in four cities were investigated three times using the Olson Enrich Marital Inventory(ENRICH), Parent-Child Cohesion Questionnaire, and Homework Effort Questionnaire. The results showed that: 1) There were significant correlations among the parents’ marital quality, parent-child cohesion, and students’ homework efforts. 2) The cross-lag analysis indicated that parents’ marital quality affected elementary school students’ homework efforts through parent-child cohesion. This research reveals the influence and the mechanism of action of parents’ marital quality on elementary school students’ homework efforts. The results of the study have enlightening significance and guidance for parents’ participation in elementary school students’ homework.