OBJECTIVE To study gender differences in different measures of iron status in infants aged 4 and 6 months old. METHODS Term delivery pregnant women with normal iron status were recruit with informed consent. Infants with normal birth weight were selected and exclusive breastfeeding were required. All infants were randomly assigned into one control group and one iron supplement group at 4 months old. The latter group were given a daily dose of iron supplement corresponding to 1 mg/kg body weight of elemental iron from 4 to 6 month. At 4 and 6 months old, vein blood were sampled to analyze hemoglobin (Hb), mean cell volume (MCV), serum ferritin (SF), and soluble transferrin receptors (sTfR) and the growth indices were measured. RESULTS Data of infants at 4 months old (n = 178) and 6 months old (n = 85) were collected. At 4 months old, male infants had significantly lower MCV and SF and higher sTfR, male infants had lower Hb but with no significant difference. 6 months old, the trends of differences stayed the same as at 4 months old, and MCV remained significant. CONCLUSIONS Male infants may have a higher risk to develop iron deficiency. Male infants may have a higher risk to develop iron deficiency. There needs to be respective diagnostical cut-off values and dietary iron requirement for male and female infants. At the same time, correct feeding is necessary.