Objective: To investigate the mediating role of children s sleep quality in the association between mother-child relationship and the executive function of preschool children, providing a reference for promoting the development of the executive function of preschool children. Methods: A stratified cluster sampling method was used to select 842 preschoolers from 12 kindergartens in Wuhu City, Anhui Province in December 2021 as the subjects of the first follow up study with follow up every six months thereafter. Finally, 746 children were included in the study after 3 follow up. Spearman correlation analysis was used to explore the associations among mother-child relationship, sleep quality and executive function in preschool children. Bootstrap program and PROCESS software were applied to test the mediating effect of sleep quality in the association between mother-child relationship and the executive function of preschool children. Results: Conflictual mother-child relationship was positively correlated with the total score of executive function, as well as scores of inhibitory, shifting, emotional control, working memory, and organizational planning ( r=0.40, 0.37, 0.36, 0.41, 0.38 , 0.34, all P <0.05). Dependent mother-child relationship was positively correlated with the total score of executive function, as well as scores of inhibitory, shifting, emotional control, working memory , and organizational planning ( r=0.23, 0.20, 0.21, 0.22 , 0.22, 0.19, all P <0.05). Sleep quality was positively correlated with the total executive function score ( r=0.27, P <0.01). After adjusting for confounding factors, sleep quality played a partial mediating role in the associations between dependent and conflictual mother-child relationships and executive function, the mediating effects were 19.40% and 11.22% respectively. Conclusions Sleep quality plays a mediating role in the association between mother-child relationship and the executive function of preschool children. Improving sleep quality in the early stage can promote the executive function of preschool children.