Objective To obtain an early indicator of marrow reaction in iron therapy of IDA by observing the change of absolute reticulocyte count(RET#),mean reticulocyte corpuscular volume(MCVr)?reticulocyte hemoglobin content(CHr)?reticulocyte hemoglobin concentration mean(CHCMr) from patients with iron deficiency anemia(IDA). Method Reticulocyte and other red blood cell indices in 13 patients with iron deficiency anemia(IDA) were determined on Advia 120 hematology analyzer during follow up of iron therapy .Results After iron therapy,RET#,CHr,MCVr significantly increased( P <0 01)at the 4 th day,back to normal at the 7 th day.Hemoglobin(Hb) significantly increased ( P <0 01) at the 14 th day,back to normal at the 28 th day.Mean corpuscular volume(MCV),hemoglobin content of red blood cell(CH) and cell hemoglobin concentration mean (CHCM) significantly increased( P <0 01) at the 28 th day,back to normal at the 49 th day.Red cell volume distribution width(RDW) significantly increased( P <0 01) at the 7 th day and then,gradually decreased after 14 days,back to normal at the 120 th day.Conclusion RET#,CHr and MCVr are the most sensitve indicators to evaluate the effect of iorn therapy on bone marrow from IDA patients.