Objective To investigate the body mass index (BMI) distribution of infants in urban Chongqing, and to explore the related factors of high BMI status. Methods A total of 31 902 (17 511 boys and 14 391 girls) infants aged from seven months to two years old, who received child heath care in Department of Child Health Care, the Children's Hospital of Chongqing Medical University from January 1^st, 2010 to November 1^st, 2014 were participants. The body mass, length, social demography, birth and infant feeding information were all collected. Chi-square test, Pearson correlation and logistic regression models were used for statistical analysis. Results The rate of high BMI status was 16.1% in infants aged seven months to two years old in our study, with the number of boys being significantly more than that of the girls (18.1% vs 13.5%, P<0.01). High BMI status in infants were associated with urban living, macrosomia, caesarean, high education level of parents and breast feeding (P<0.01). The multiple logistic regressions showed that age, gender, region of living, birth mass, delivery mode,gestational age and parents' education level were associated with high BMI status in infants aged from seven months to two years old (P<0.01) . Conclusion Birth mass, feeding patterns, age, gender and region are important factors for high BMI status in infants. Childhood obesity prevention should be prevented from many aspects.