Abstract Objective To study the correlation between neck circumference and body mass index and the value of neck circumference in identifying overweight and obesity in preschool children. Methods The stratified cluster sampling method was used to recruit 3 719 children under 7 years from 10 kindergartens in Urumqi, China. General data were collected, and physical measurements were performed. A Pearson correlation analysis was used to evaluate the correlation between neck circumference and body mass index. The receiver operating characteristic (ROC) curve was used to assess the accuracy of neck circumference in identifying overweight/obesity. The Kappa consistency test was used to assess the consistency of neck circumference and body mass index in identifying overweight/obesity. Results There was a positive correlation between neck circumference and body mass index in boys and girls of all ages (r≥0.50, P<0.001). According to body mass index as the criteria for overweight/obesity, the children were divided into an overweight/obesity group and a non-overweight/obesity group, and the analysis showed that the overweight/obesity group had a significantly larger neck circumference than the non-overweight/obesity group (P<0.001). The ROC curve analysis showed that neck circumference had an area under the ROC curve of >0.7 in identifying overweight/obesity for boys and girls. The Kappa consistency test showed that the neck circumference and body mass index had a Kappa value of >0.40 in identifying overweight/obesity in boys and girls of all ages. Conclusions Neck circumference is positively correlated to body mass index, and neck circumference can be used to identify overweight/obesity in preschool children.