Objective: Serving as a common hypertensive target organ damage, left ventricular (LV) structure alteration has been found to be associated with cognition decline in the elderly. However, its mediating role in the association between decreased cognitive function and elevated blood pressure (BP) remains controversial, owing to several inherent confounder in adults that could distort observed associations. The study was first known conducted to examine the association between LV structure, BP and cognitive function in preschool-aged children, a population without disturbance of various cardiovascular risk factors. Methods: This study included 1279 children from Shanghai Birth Cohort (SBC) during 2018 to 2021. Using the Wechsler Preschool and Primary Scales of Intelligence-Fourth Edition (WPPSI-IV), children’s intelligence quotient (IQ) was evaluated at 4-year-old. Detailed anthropometrics and BP measurements and echocardiography were conducted during follow-up. Multivariable linear regression models and restricted cubic spline were applied to estimate the association between individual BP, LV structure parameters and IQ scores. Results: There was no significant association found between cognitive function and LV structure in preschool-aged children, while higher BP levels was found to be correlated with lower scores in cognitive function. Children in the elevated BP and non-LVH group tended to have lower full-scale IQ (FSIQ). In detail, children with elevated BP tended to have lower scores in FSIQ (β: -2.95, 95%CI: -4.65, -1.25), processing speed index (β: -1.77, 95%CI: -3.41, -0.14), working memory index (β: -2.79, 95%CI: -4.70, -0.88) and visual spatial index (β: -2.64, 95%CI: -4.74, -0.55), and these associations were independent of LV structure. Conclusion: Higher BP levels was related to poor cognitive development during childhood as early as four, while LV structure alteration was not. The associations between BP and children’s decreased cognitive function was independent of LV structure.