Objective To explore the effect of nanometer calcium carbonate on the efficacy of calcium supplement.Methods Forty 3-week old weaning SD rats were randomly divided into four groups:basal low calcium group,calcium carbonate group,calcium amino acid chelate group and nanometer calcium carbonate group,half male and half female.They were fed 28d.Results The femur weight, femur length and serum calcium were higher in the supplemented with calcium groups than that in the basal low calcium group.The femur weight and femur length of calcium amino acid chelate group and nanometer calcium carbonate group had significant differences compared with basal low calcium group(P0.05).There were significant differences of serum calcium concentration between the supplemented with calcium groups and basal low calcium group(P0.05).Conclusion Nanometer calcium carbonate is a good calcium resource and can be used in food additives and medicines.