Abstract: Objective To understand the changes in low hemoglobin count and its relationship with body mass index (BMI) in Ningxia children. Methods A total of 7 671 children aged 7, 9, 12 and 14 years old were selected from the Chinese National Survey on Student's Constitution and Health of Ningxia in the year of 2005 and 2014. The prevalence of low hemoglobin count in children and its relationship with BMI was analyzed. Results The prevalence of low hemoglobin significantly increased from 6.7% in 2005 to 8.8% in 2014. Percentage change from baseline was 31.3%. The percentage of male and female students with low hemoglobin was(6.4%, 6.9%) in 2005, and(8.1%, 9.4%) in 2014. The difference was statistically significant among females. Significant difference was found between urban and rural areas in both 2005 and 2014(P<0.05). The prevalence of low hemoglobin was highest in low economic regions(12.5%) in 2005, followed by moderate (3.0%) and high economic area (2.1%). The prevalence was found highest in high economic regions (10.8%) in 2014, followed by moderate (8.7%) and low economic areas (5.9%). No significant differences in prevalence of low hemoglobin were found among students with different BMI levels, however, female obesity positively correlated with low hemoglobin(OR= 2.049, 95%CI = 1.14-3.67). Conclusion The increasing trend in low hemoglobin prevalence is observed, especially among girls, rural areas and Hui ethnic students.