Background Renal clear cell carcinoma (RCCC) is the most common malignant renal tumor. It is highly malignant,does not cause clinical symptoms in its eady stages, and cannot be diagnosed using conventional ultrasound. This study was aimed to investigate the contrast-enhanced ultrasound (CEUS) mode and characteristics of the time-intensity curve for RCCC and its pathological basis.Methods Forty-two patients with pathologically diagnosed RCCC underwent CEUS examination before surgery. The patients kidneys were visualized after injection of contrast agents using the Technos MPX DU8. We analyzed the CEUS mode, time-intensity curve, and pathological findings.Results The detection rate of RCCC with conventional ultrasound was about 71%, while the rate using CEUS was 100%. Larger tumors (33 cases) showed non-uniform enhancement with defective filling. CEUS modes were divided into 4 types: type Ⅰ, "quick in and out" (26.19%, 11/42); type Ⅱ, "quick in and slow out" (40.48%, 17/42); type Ⅲ, "Simultaneous in and out" (16.67%, 7/42); and type Ⅳ "slow in and out" (16.67%, 7/42). All types had a close correlation to the pathological basis. "Time-intensity curve of CEUS consisted of 3 phases, the perfusion phase, regression phase, and lag phase. Cases of types Ⅰ and Ⅲ only had a perfusion and regression phase, those of type Ⅱ and Ⅳ had a perfusion phase,regression phase, and lag phase. Quantitative analysis of the time-intensity curve showed that the time-to-peak (TTP) of the lesions was shorter than that of normal renal parenchyma (P