Abstract: Iron fertilizer can not satisfactorily correct chlorosis when fertilized in the soil, as Fe2+ in the fertilizer is easily oxidized into Fe3+ in the soil. High-pressure trunk-injection of iron fertilizer was reported to be effective to correct chlorosis, but the mechanism involved was unknown. The objective of this paper was to better understand the mechanism of correcting chlorosis with iron fertilizer by using high-pressure trunk-injection method.The experiments were carried out with apple (Malus pumila, cultivar Fuji) during the year 2000-2002 at experimental station of Quzhou of China Agricultural University and in the Yongnian county of Hebei province. The N - Fe, O-phenanthroline-Fe and 59Fe were injected through the tree trunk. The results indicated that Fe2+ was transported along the central xylem, and most of Fe2+ was stored in roots due to the difficulties in root to shoot transportation of Fe2+. Regreening in iron deficiency chlorosis trees was slower but the effect of correcting iron deficiency chlorosis lasted longer when iron fertilizer was injected than was root-supplied.