Objective To investigate the application of quantitative CT (QCT) and magnetic resonance imaging (MR) in the diagnosis of nonalcoholic fatty liver (NAFLD). Methods 67 cases of NAFLD patients (NAFLD group) who were treated in our hospital from February 2016 to August 2017 were selected and 70 healthy volunteers were selected as the control group, QCT and MR scans were performed in all two groups,the fat content of the liver was measured by QCT corrected calculation formula (Fat% QR),the liver fat fraction (Fat% MR) was measured by MR. Results The Fat% QR and Fat% MR in NAFLD group were (20.10±10.04)% and 17.32 (12.01, 23.10)%, which were significantly higher than those in the control group (P<0.05). There was no significant difference in Fat% QR and Fat% MR between men and women in NAFLD group (P>0.05). The area under the ROC curve of Fat% QR and Fat% MR in diagnosis of NAFLD were 0.924 and 0.856, and P<0.05. When the cut-off value of Fat% QR was 10.16%, the sensitivity and specificity of the diagnosis of NAFLD were 80.60% and 94.29%. When the cut-off value of Fat% MR was 14.05%, the sensitivity and specificity of the diagnosis of NAFLD were 73.10% and 91.43%. Fat% QR was positively correlated with Fat% MR (rs=0.722, P<0.05). Conclusion QCT and MR have a certain value in the diagnosis of NAFLD, and the diagnostic value of QCT is high.