Objective To evaluate the application value with Energy Spectrum CT multi -parameter quanti-tative value in differentiating pulmonary occupying lesions (>0.5cm in diameter).Methods Those were retrospec-tively analyzed on 58 cases in pulmonary occupying lesions performed spectrum dual -phase enhanced CT scan and confirmed by pathology,including malignant group 48 cases;10 cases of benign group.Iodine content(IC)was meas-ured in arterial phase(AP)and venous phase (VP)in iodine based on the image and the level of the aorta,and nor-malized iodine concentrations were calculated in the two phases lesions compared with aorta,and the difference between the two normalized iodine concentrations ICD (ICD =NICvp -NICap).To measure the CT value of lesions on 50keV and 100keV energy image,and calculate the energy attenuation curve slope,namely |Hu (100 kev -50kev)/Hu50 |.The differences of NIC,curve slope,and ICD were compared between benign and malignant pulmonary occupying lesions using independent sample t test method.Results In two phase scan,NIC,curve slope of the venous phase and ICD in malignant group were significantly higher than the benign group,(NIC,curve slope of the venous phase and ICD of the malignant group:NICap:0.180 ±0.051,NICvp:0.463 ±0.086,1.696 ±0.475,ICD:0.284 ± 0.071;NIC,curve slope of the venous phase and ICD of the benign group:NICap:0.123 ±0.062,NICvp:0.290 ± 0.119,1.169 ±0.582,ICD:0.166 ±0.073,),but there was no significant difference between the patients with benign and malignant lesions in curve slope of the arterial phase.Conclusion Energy spectrum CT dual -phase enhanced scan can differentiate the nature of benign and malignant pulmonary occupying lesions,and has certain clinical application value.