Abstract: Objective　To explore the clinical application value of CT values in upper urinary tract calculi with pyelonephritis and pyonephrosis. Methods　The retrospective analysis was performed on 157 patients with renal infection caused by upper urinary tract calculi admitted to the hospital from March 2015 to January 2020. According to the clinical manifestations and auxiliary examinations, the patients were divided into three groups: simple hydronephrosis group (n=73), acute pyelonephritis group (n=58) and pyonephrosis group (n=26). All patients underwent multi-slice spiral CT plain scanning, and the CT values of renal pelvis hydrops were measured, calculated and compared in the three groups. The receiver operating curve (ROC) was drawn to search the optimal critical CT value as the diagnostic basis for identifying pyelonephritis andpyonephritis. Results　CT values of the simple hydronephrosis group, acute pyelonephritis group and pyonephrosis group increased in turn: (2.85±1.7) HU, (9.21±4.8) HU and (17.69±4.2) HU, respectively. There were significant differences between the three groups (F=175.127, P＜0.05). The area under ROC curves of CT values of renal pelvis hydrops in identifying pyelonephritis and pyonephrosis was 0.897, and the 95%CI was 0.812-0.953. When the CT value of renal pelvis hydrops was 12 HU, the Youden index was the largest (0.768), the sensitivity was 84.48% and the specificity was 92.31%. Conclusion　CT values accurately reflect the disease progression of pelvis infection caused by upper urinary tract calculi, and which has early clinical diagnostic value in identifying pyelonephritis and pyonephrosis.