The object of the present study was to investigate the levels of serum transferrin receptor (sTfR) and its response to Fe supplementation in Fe-deficient children and the role of sTfR in detecting Fe deficiency and assessing the efficacy of Fe supplementation. According to the diagnostic standard, 1006 children, aged 6–14 years in Fangshan district, Beijing, Peoples Republic of China, were divided into four groups: normal; Fe store depletion (IDs); Fe deficiency erythropoiesis (IDE); Fe deficiency anaemia (IDA). sTfR was determined and transferrin receptor-ferritin (TfR-F) index was calculated in 238 children, sixty-four normal and 174 Fe deficient. Children were administered a NaFeEDTA capsule containing 60 mg Fe once per week for the IDs and IDE groups and three times per week for the IDA group for nine consecutive weeks. The parameters reflecting Fe status and sTfR were determined before and after Fe supplementation. The levels of sTfR and TfR-F index in Fe-deficient children were significantly higher than those in the normal group. The receiver operating characteristic curve showed that sTfR has proper diagnostic efficacy for functional Fe deficiency. After Fe supplementation, the level of sTfR was significantly decreased in children with IDs, but not in children with IDE and IDA, while TfR-F index was significantly decreased in Fe-deficient children. sTfR is a reliable indicator for detecting functional Fe deficiency, and TfR-F index is a sensitive parameter for assessing the efficacy of Fe supplementation.