Abstract: Objective　To investigate the role of iron deposition on white matter demyelination in rats with delayed encephalopathy after acute carbon monoxide (CO) poisoning (DEACMP). Methods　SD rats screened by water maze experiment were divided into air control group (AC group), CO poisoning group (CO group) and deferriamine (DFO) + CO poisoning group (DC group). Each group was further divided into 5 subgroups including day 1, 3, 7, 14 and 21 groups. The DEACMP model was prepared by intraperitoneal injection of CO gas in rats of CO group and DC group. Rats in DC group were intraperitoneally injected with 100 mg/kg of deferriamine 1 h before modeling, and injected once a day after modeling. Rats in AC and CO groups were intraperitoneally injected with the same amount of normal saline. Morris water maze and HE staining were used to observe the changes of the behavior and pathological neurons of rats before and after exposure. Prussian blue staining was used to detect the expression of iron. The expression of ferritin (Fn) and basic myelin protein (MBP) were detected by Western blot assay. The expression of 2', 3' -cyclic nucleotide phosphodiesterase (CNPase) was detected by immunohistochemical staining and the expression of MBP was detected by immunofluorescence staining. Results　After 14 days of exposure, the escape latencies were longer in CO and DC groups than those in AC group, and the escape latency was shorter in DC group than that in CO group. The times of crossing the platform were significantly lower in CO group than those in AC and DC groups (P＜0.05). The cell degeneration and necrosis were found in CO group at 14 days after infection. The cell degeneration and necrosis in the DC group were between AC and CO groups (P＜0.05). The expression of iron reached the peak on 14 days in CO group (P＜0.05). Compared with CO group, the expressions of iron and Fn decreased in DC group, and the expression of MBP increased after 3 days of exposure in DC group, and the expressions of CNPase increased at 14 and 21 days (P＜0.05). The myelin arrangement was denser in DC group than that in CO group, and the expression of MBP was increased. Conclusion　After acute CO poisoning, excessive deposition of iron may lead to progressive demyelination of the white matter in rats by reducing the expressions of CNPase and MBP, and damaging oligodendrocytes (OLs), resulting in delayed cognitive dysfunction.