The purpose of this study were to investigate the effect of rapid weight loss and iron supplementation on blood components and exercise capacity in female athletics. The 20 female athletics of university, who were participated in the subjects of this study, and were divided into 3 groups: weight loss and iron supplementation group(WL+IS group: n=6), weight loss group(WL group: n=8), nonweight loss group(NWL group: n=6). Weight loss was achieved in 3 days by a diet restriction and forced to use wearing suit for sweating during exercise time. The results of this study run as follows: Weight of the Wl+IS and WL group were decreased each 4.3%, 3.9%. RBC, Hb, Hct levels improved significantly after weight loss in the WL group but was not significant in the WL+IS and NWL groups. Ferritin, transferrine levels improved after weight loss in the WL+IS and WL groups but transferrine was not significant in the WL+IS group. Endurance time and peak power highly decreased after weight loss in the WL, but Vo₂max and mean power not effected by rapid weight loss. And Vo₂max and peak power in the WL+IS group improved not significantly after weight loss and endurance time decreased not significantly decreased after weight loss in the WL+IS group. Therefore, the results suggested that iron supplementation during rapid weight loss in female athletics could have the positive effects of exercise capacity but blood components(RBC, Hb, Transferine) were not significantly affected by iron supplementation.