Objective: To investigate the interactive effects of prenatal and postnatal factors on overweight and obesity in preschool children, so as to provide evidence for subsequent planning of prevention strategies and intervention measures. Methods: Between October 2020 and June 2021, a convenience cluster sample of 918 preschool children from four kindergartens in Xuzhou urban area underwent questionnaire surveys and physical examinations. The Chi square test was used to compare intergroup differences in overweight and obesity prevalence. Multivariate Logistic regression analysis was employed to investigate the effects of prenatal and postnatal factors, as well as their interactions, on overweight and obesity in preschool children. Results: The prevalence of overweight and obesity among preschool children was 30.8%, with boys exhibiting a higher rate (37.0%) than girls (24.8%). Statistically significant differences in overweight and obesity prevalence were observed across age groups, genders, paternal pre pregnancy body mass index (BMI), paternal educational level, delivery mode, antibiotic use within the six months after birth, and rapid weight gain during infancy ( χ 2=5.08-17.67, all P <0.05). After adjusting for confounding factors such as age, gender, the only child, parental educational level and parental average monthly income, interaction analysis revealed that when the father was overweight or obese before conception, children delivered by caesarean section had an increased risk of overweight or obesity ( OR= 2.05 , 95%CI =1.02-3.39), and children with rapid weight gain during infancy also had an increased risk ( OR=2.05, 95%CI = 1.08 -3.88) (both P <0.05). Gender stratified analysis revealed that the interaction between paternal pre pregnancy BMI and mode of delivery on overweight and obesity was more pronounced among girls ( OR=4.00, 95%CI=1.51-10.58, P <0.05). While the interaction between the father s pre pregnancy BMI and rapid weight gain during infancy was more pronounced in boys ( OR= 2.85 , 95%CI=1.14-7.08, P <0.05). No significant interactions between prenatal and postnatal factors on overweight and obesity in preschool children were observed (all P >0.05). Conclusions Multiple prenatal and postnatal factors influence overweight and obesity in preschool children. Attention should be paid to mode of delivery and infant weight gain, particularly when the father is overweight or obese, to reduce the risk of overweight and obesity in preschool children.