Objective The aim of this study was to evaluate the benefits of i.v. iron therapy in iron-defi-cient patients with left ventricular ejection fraction preserved heart failure (HFpEF). Methods 61 HFpEF pa-tients with iron deficiency were randomized to treatment with or without i.v. iron,as ferric carboxymaltose(FCM, n = 31)or placebo(saline,n = 29)for 24 weeks of a double-blind,placebo-controlled trial. The primary end-point was the change in 6-min-walk-test(6MWT)distance from baseline to Week 24. Secondary end-points includ-ed changes in New York Heart Association(NYHA)class,health-related quality of life(QoL),with NT-proBNP under observation. Results Compared with the control group at week 16 and 24,the iron treatment group has much more improve in 6MWT and the health-related quality of life(HRQoL)(P<0.05). The changes in NT-proB-NP level and NYHA heart function classification only show significance at week 24(P<0.05)but not at week 16 (P>0.05). Conclusion In this study,Treatment with intravenous ferric carboxymaltose can improve symptoms, functional capacity,and quality of life.