ObjectiveTo describe severity of anemia and explore its determinants among children under 36 months old in rural western China.Study DesignThe family information of 6711 children was collected and their hemoglobin was measured in 2005. A generalized estimated equation (GEE) linear model was used to identify the determinants of severity of childhood anemia.ResultsThe prevalence of mild, moderate and severe anemia among these children was 27.4%, 21.9% and 3.2% respectively. GEE model analysis showed that province-level region and severity of maternal anemia affected the severity of childhood anemia not only in 0–5 months but also beyond 5 months. In addition, children aged 0–5 months in families using iron pot (coefficient = −0.26 95%CI −0.41,−0.12) had seldom more severe anemia, and children aged 6–36 months in families more than 4 members (coefficient = −0.03 95%CI −0.06,−0.01) or of Han ethnicity (coefficient = −0.08 95%CI −0.13,−0.04) seldom had more severe anemia but boys (coefficient = 0.03 95%CI 0.01,0.06) or younger children (6–11 month vs 30–36 month: coefficient = 0.23 95%CI 0.17, 0.28; 12–17 month vs 30–36 month: coefficient = 0.19 95%CI 0.15,0.24; 18–23 vs 30–36 month: coefficient = 0.09 95%CI 0.04,0.13) had more severe anemia.ConclusionThe prevalence of moderate-to-severe anemia in these children was about 25%. Province-level region, iron pot use, family size, ethnicity, age and gender of children and severity of maternal anemia were important determinants of the severity of childhood anemia. These findings have some important implications for health policy decision for childhood anemia in rural western China.