Objective To investigate the prevalences of metabolic syndrome (MS) and MS components in children with normal weight, overweight and obesity, and to explore the relationship between MS and family factors, eating behaviors and diet factors. Methods A total of 1 707 children from one primary school of Luwan District and one primary school of Baoshan District in Shanghai were selected, and 364 children with overweight and obesity were screened. Ninety-four venous blood samples were available from these 364 children, and overweight group (n=34) and obesity group (n=60) were divided. Besides, control group of children with normal weight was established (n=120). With case-control method, the influencing factors of MS were analysed by questionnaire survey, physical examinations, blood pressure and blood biochemical marker measurement. Results The prevalences of overweight and obesity in 1 707 children were 12.8% and 9.1%, respectively. Both the overweight rate and obesity rate in boys were significantly higher than those in girls (P=0.000). Both the overweight rate and obesity rate of children in Luwan District were significantly higher than those of children in Baoshan District (P=0.000). By Cook diagnostic criteria, the prevalences of MS in control group, overweight group and obesity group were 0.8%, 2.9% and 6.7%, respectively. In children of obesity group, the prevalences of abdominal obesity, hypertension, high triglyceride and low high density lipoprotein-cholesterol were 76.7％, 46.7％, 11.7％ and 6.7％, respectively, and those with one, two and three MS components accounted for 51.7%, 35.0% and 6.7%, respectively. Multivariate analysis revealed that protein, calcium, vitamin C and vitamin E were protective factors of MS components, while parental obesity, taking food too fast, big appetite and cooking by grandparents were risk factors of MS components. Conclusion The prevalence of MS is high among investigated children. Family factors, eating behaviors and diet factors are related to MS components.