Objective To explore the association of family socioeconomic status (SES) with growth, development and nutritional status of children under 3 years old, so as to provide scientific basis for the prevention and health care of children in China. Methods Data were from the database of Xi'an based on the physical development survey of children under 7 years old in nine cities of China in 2015. Socioeconomic status comprehensive indicators included parents'education level, parents'occupation and annual family income. The outcome variables included physical measurement (length and weight) and nutritional status.After adjusting children's gender and month agelinear regression models and Logistic regression models were established to analyze the association between SES and children growth and nutritional outcomes. Results A total of 12 017 children under 3 years old were included in this study, among which 281 (2.3%) children were assessed with malnutrition and 531 (4.4%) children were assessed with overnutrition. After adjusting children's gender and month age, compared with children with low levels of SES, children with moderate levels of SES increased in length by 0.32 cm (95% CI: 0.16 - 0.47) and had a 20% lower risk of overnutrition (OR=0.80, 95%CI: 0.65 - 0.98). Children with high levels of SES increased in length by 0.77 cm (95%CI: 0.61 - 0.92) and weight by 0.06 kg (95% CI: 0.006 - 0.12) and a 33% reduction in the risk of overnutrition (OR=0.67, 95% CI: 0.53 - 0.83). Conclusions Better SES may reduce the risk of overnutrition in children, and contribute to children's physical development and nutritional health. Efforts should be made to improve the family parenting environment, as well as to strengthen the propaganda and education of children's health care in low SES families, thus improving the health level of children.