Objective: The purpose is to verify that whether there are significant correlation between parent-teacher cooperation, quality of home environment, and mathematical interaction of parents and cognitive development of 3-year-olds, and the quality of home environment and mathematical interaction mediate the relationship between the parent-teacher cooperation and the cognitive development. Methods: A test was performed on 110 3-year-olds enrolledin a daycare center located in city S, and a questionnaire survey was conducted on their parents. We analyzed our data using SPSS WIN 21.0 and pearson’s correlation, tested the mediating effect using regression, and used the Sobel test to check significance of the mediating effect. Results: Cognitive development of 3-year-olds was correlated with the parent- teach er cooperation, the quality of home environment, and mathematical interaction of parents. The quality of home environment showed complete mediating effect on the relationship between the parent-teacher cooperation and the cognitive development, and the mathematical interaction showed complete mediating effect on the relationsh ip between the parent-teacher cooperation and the cognitive development. Conclusion/Implications: The parent-teacher cooperation indirectly predicts the cogni tive development through the quality of home environment and the mathematical interaction. This research can contribute to the development of the family- institution connection program to facilitate the parent-teacher cooperation.