Abstract： Objective To study the characteristics of proton magnetic resonance spectroscopy (1H magnetic resonance spectroscopy, 1H MRS) in patients with delayed encephalopathy following acute carbon monoxide poisoning (DEACOP) and its significance in the early diagnosis of the disease. Methods MRI and 1H MRS were performed in 38 DEACOP patients and 30 healthy volunteers. The ratios of N-acetylaspartate ( NAA), Creatine ( Cr), Choline (Cho) peaks were measured in each volume of interest, and the correlation of Activity of Daily Living Scale (ADL) and Mini-Mental State Examination (MMSE) with NAA/Cr, Cho/Cr,Cho/NAA were analyzed. Results Compared with those of the control group, the NAA/Cr ratio in different parts decreased with very significant statistical differences ( P ＜ 0. 01 ), while Cho/Cr and Cho/NAA ratio increased also with very significant statistical difference ( P ＜ 0. 01 ). Negative correlation was found in the assessment scores between Cho/Cr and MMSE, ADL. Cho/NAA was also negatively correlated in the assessment scores with MMSE and ADL, and NAA/Cr was positively correlated in the assessment scores with MMSE and ADL. The NAA/Cr ratio in moderate and serious DEACOP patients decreased, when it was compared with that of the mild DEACOP patients, with statistical differences (P ＜ 0. 05 ). Cho/Cr and Cho/NAA ratio increased, when it was compared with that of the control group, with statistical differences ( P ＜0. 05). Conclusions 11 MRS could detect metabolic abnormalities in DEACOP patients with brain lesion.Abnormal changes in the ratio of metabolites might indicate poor prognosis.