Abstract: Objective: To evaluate reconstruction parameters of monochromatic image with dual-energy CT in nephrographic phase, and find the optimal monochromatic image for displaying renal solid mass. Methods: Clinical material and imaging data of 20 patients underwent dual-energy CT examination (80 kVp/Sn140 kVp) were analyzed in this study. Various monochromatic image (40 ~ 120 keV) of Dual-energy CT were generated by 80kVp image and Sn140 kVp image. The image quality was evaluated by subjective and objective assessment. The optimal CNR and SNR monochromatic images were calculated by objective assessment for comparison with linear blending image with weighted factor 0.5. Subjective image quality evaluated by using five points grading scale method for blending linear image with weight factor 0.5 and optimal monochromatic image by two experienced radiologists. Results: Twenty patients (male 13, female 7) were enrolled in this study, mean value of CTDI_vol was (11.54 ±4.09) mGy, SSDE was (14.86 ±3.97). Objective assessment: the highest CNR and SNR of monochromatic image was 60 keV and 70 keV, respectively. Significant statistical difference was existed comparison with blending linear image with weight factor 0.5, respectively (all P<0.05). Subjective assessment: There was no significant statistical difference in the whole image quality and detail of renal lesion comparison with blending linear image with weight factor 0.5 (all P>0.05). Conclusions: Monochromatic images of 60 keV and 70 keV could get highest CNR and SNR for detection of renal solid mass, respectively, which were superior to linear blending images (M= 0.5). However, Monochromatic images of 60 keV and 70 keV were equivalent to display the whole image quality and detail of renal solid mass.