Objective To investigate the brain MRI features of patients with acute carbon monoxide poisoning encephalopathy (ACOP) and the clinical value of analyzing apparent diffusion coefficient (ADC) value. Methods The brain MRI imaging and clinical data of 46 cases of patients with delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) (the observation group) and 30 cases of healthy volunteers (the control group) were retrospectively analyzed. The imaging features were analyzed. The differences of ADC average values on the same sites in cortical areas, centrum semiovale, periventricular white matter and globus pallidus areas were compared. Results Among 46 subjects in the observation group, the MRI findings of 15 cases (32.6%) were normal (no patients with severe ACOP, 14 mild cases, 1 moderate cases). The MRI findings of the other 31 subjects showed abnormal signal, including 2 cases of cerebral cortex involvement. There existed symmetrical low signal in on bilateral parietal cortex on T1WI and symmetrical high signal on T1WI and DWI. 19 cases showed abnormal signal in the bilateral globus pallidus area, showing symmetrical long T1 and long T2 signal, with typical panda eyes features;10 cases showed abnormal signal in bilateral cerebral white matter area. MRI showed symmetrical distribution images of patchy abnormal signal shadow, slightly low signal on T1WI and slightly high signal on T2WI. There were no abnormalities in cerebral sulcus and cerebral fissure. The mean values of ADC in the cortical areas, centrum semiovale, periventricular white matter and globus pallidus areas of the observation group were significantly lower than those of the control group(P<0.05). Conclusion MRI has obvious imaging characteristics in the clinical diagnosis of DEACMP. Its combination with ADC value in assessment can effectively improve the accuracy of diagnosis, and provide conditions for the smooth development of the follow-up diagnosis and treatment.