Objective: To understand the working mechanism and the relationships among the quality of teacher-child interaction (TCI), children's comprehensible vocabulary (CV) and executive function (EF). Methods: Using stratified sampling, 900 children (boys 50.2%) and 60 preschool teachers were recruited from 4 places in China for testing, and five measurement tools, including the Classroom Assessment Scoring System (CLASS), the Peabody Picture Vocabulary Test (PPVT-R), the Stroop test, a card sorting task, and the Wechsler Intelligence Scale for Children (WISC-IV), were used. Results: For every additional unit of TCI, EF increases by 0.55 units; For every additional unit of EF, CV increases by 0.55 units; For every additional unit of CV, EF increases by 0.55 units; For every additional unit of CV, TCI increases by 0.38 units; For every additional unit of TCI, CV increases by 0.38 units. In the Model of TCI-EF-CV, the estimated value of TCI and the total effect of comprehensible vocabulary is 0.18; Z = 9.84, which is significantly greater than 1.96 at the bias-corrected 95% confidence interval and at the percentile 95% confidence interval (0.15, 0.23), both of which do not contain 0. The direct effect of TCI and CV is significant and indirect effects account for 39%. In the Model of TCI-CV-EF, the total effect of TCI on executive function is 0.09 (Z = 6.14), the direct effect is not significant with bias-corrected 95% confidence interval and 95% confidence interval (−0.01, 0.03), both of which include 0. Conclusion: There are two-way effects among children's EF and CV, TCI and CV. EF plays a mediating role in the influence of TCI on CV. TCI positively predicts children's EF, but this mainly depends on CV. Therefore, TCI plays a positive role in the development of children's CV and EF.