Objective To explore the feasibility of second-generation dual-layer detector spectral CT ab-dominal virtual non-contrast(VNC) for diagnosing fatty liver.Methods The imaging data of 128 patients with second-generation dual-layer detector spectral CT abdominal enhanced CT in West China Hospital of Si-chuan University from June 2022 to December 2022 were retrospectively analyzed.The CT values of the left lobe,right anterior lobe,right posterior lobe and spleen of all patients were measured on TNC,arterial stage VNC (A-VNC) and venous stage VNC (V-VNC) images.The difference value (L-S) and ratio value (L/S) between the CT value of liver and CT value of spleen were calculated.According to the threshold value of TNC image diagnosis of fatty liver in previous studies,the included cases were divided into two groups:fatty liver group and non-fatty liver group.The Mann-Whitney U test was used to compare the difference of quanti-tative parameters between the fatty liver group and non-fatty liver group.The efficiency of VNC in the diagno-sis of fatty liver was evaluated by the receiver operating characteristic (ROC) curve,and the difference be-tween ROC curves was compared with DeLong's test.The intra-group and inter-group correlation coefficient (ICC) values were used to evaluate the consistency of data measurement.Results The ICC values of intra-group and inter-group consistency of data ranged (0.835-0.986) and (0.810-0.978),respectively (P<0.05).The mean value of left lobe,right anterior lobe,right posterior lobe and triple lobe of liver and CT val-ue of spleen in A-VNC and V-VNC images were lower than those of TNC images,and the differences were statistically significant (P<0.05).The CT values of TNC,A-VNC,V-VNC,(L-S) values and (L/S) values of the non-fatty liver group were higher than those of the fatty liver group,and the differences were statistical-ly significant (P<0.05).The CT value,(L-S) value and (L/S) value of TNC,A-VNC and V-VNC images in the non-fatty liver group were higher than those in the fatty liver group,and the differences were statistically significant (P<0.05).The area under the curve (AUC) of CT values of A-VNC and V-VNC for the diagnosis of fatty liver all were 0.997,and their efficiencies for diagnosing fatty liver had no statistical difference (Z=0.407,P=0.684).AUC of A-VNC (L-S) and V-VNC (L-S) in the diagnosis of fatty liver was 1.000 and 0.981,respectively,and their efficiencies for diagnosing fatty liver had no statistical difference (Z=1.790,P=0.074).AUC of A-VNC (L/S) and V-VNC (L/S) in the diagnosis of fatty liver was 0.992 and 0.987,respec-tively,and their efficiencies for diagnosing fatty liver also had no statistical difference (Z=0.665,P=0.506). Conclusion The CT values of liver and spleen in VNC images reconstructed by second-generation dual-layer detector spectral CT are lower than TNC,but it is still feasible to diagnose fatty liver based on VNC images.