Purpose To evaluate the value of MRI T1 mapping combined with biliary tract paravertebral muscle signal intensity ratio in liver function.Materials and Methods A total of 72 patients with Gd-EOB-DTPA enhanced MRI were prospectively collected in Beijing Friendship Hospital from August 2020 to February 2022 and divided into three groups according to Child-Pugh classification of liver function:22 patients in normal liver function group,35 patients in grade A group and 15 patients in grade B+C group.The T1 mapping sequence was scanned in all patients before and 20 min after enhancement to measure the pre-enhancement and post-enhancement(T1post)T1 relaxation time of liver parenchyma,and the reduction rate of liver T1 relaxation time(ΔT1)was calculated.Biliary tract signal and paravertebral muscle signal were measured on hepatobiliary stage images,and biliary tract paravertebral muscle signal intensity ratio(SIR)was calculated.The consistency of measurement results among physicians was evaluated.The correlation between each index and liver function grade was observed.The differences among different groups were compared.The diagnostic efficiency of each image index were evaluated.Results T1post was positively correlated with liver function grade(r=0.683,P<0.001),and it increased gradually with the severity of liver function impairment.ΔT1,SIR,SIR×ΔT1 were negatively correlated with liver function grade(r=-0.764,-0.729,-0.826,all P<0.001),and gradually decreased with the severity of liver function impairment.T1post,ΔT1,SIR,SIR×ΔT1 had statistical significance in liver function classification among all groups(F=27.491,55.782,48.410,46.809,all P<0.05).In pairwise comparison,the differences of each index were also statistically significant(P<0.05).The best diagnostic efficacy of each index was SIR×ΔT1,and the area under the curve of normal liver function group and cirrhosis group,grade A group and grade B+C group were 0.915 and 0.984,respectively.Conclusion T1post,ΔT1,SIR and SIR×ΔT1 are strongly correlated with Child-Pugh grade of liver function.SIR×ΔT1 can be used as an imaging index for quantitative evaluation of liver function.