Objective To understand current status and the correlation of dietary behavior and body mass index(BMI) in children aged 3-6 years,so as to provide references for the prevention and treatment of malnutrition in children. Methods A stratified cluster sampling method was carried out in 486 main caregivers of children from September 2017 to January 2018.Participants were asked to fill out Preschool Children's Diet Behavior Scale. And data on children's height,weight and body mass index(BMI) were collected. χ² test,independent sample t test and multivariate Logistic regression were used to analyze data. Results Totally 356(73.25%) children with normal BMI,11(2.26%) emaciated children,61(12.55%) overweight children and 58 obese children were detected in 486 children. There was no significant difference on scores of all dimensions of dietary behavior between boys and girls in children aged 3-6 years(P>0.05). And the scores of emotional diet and active eating ability at different age groups were significantly different(F=3.472,3.816,P<0.05). Also,there were statistically significant differences on the scores of picky eating,bad eating habits and satiety response(F=4.804,6.077,4.392,P<0.05) with children different BMI values. Picky eating(OR=-0.367,95%CI:-0.966--0.112,P<0.001) and bad eating habits(OR=-0.097,95%CI:-20.705--0.204,P＝0.045) had impact on children's BMI. Conclusions There are nutritional problems such as obesity,overweight and emaciation in children aged 3-6 years in this district. Picky food,bad eating habits affect children's BMI. Children in different BMI groups have different eating behaviors on the aspects of picky eating,bad eating habits and satiety response.