Abstract： 【Objective】To evaluate the relationship between apparent diffusion coefficient（ADC）and histopatho? logical differentiation of clear cell renal cell carcinoma（CCRCC）.【Methods】In this retrospective analysis，we investigat? ed 63 patients with CCRCC confirmed by pathology. 63 patients who had were grouped according to the Fuhrman patholog? ical grading system，fromⅠtoⅣ. Four grades were merged into three classifications consisting of well-differentiated CCRCC（ⅠandⅡ），moderatedly-differentiated CCRCC（Ⅲ）and poorly-differentiated CCRCC（Ⅳ）. Magnetic reso? nance examinations of magnetic resonance imaging（MRI） plain scan，LALA dynamic enhanced scan and diffusion weighted imaging（DWI）（1.5T，b value：800 s/mm2）were performed. The each ADC value was measured. ANOVA was used to compare ADC values between the three different histopathological groups. Spearman correlation analysis was used to analyze the correlation between histopathological differentiation of CCRCC and ADC values. A receiver operating curve （ROC）analysis was performed to evaluate the diagnostic efficiency of ADC values.【Results】The ADC value（10-3 mm2/s） of well-differentiated，moderately differentiated and poorly-differentiated CCRCC was 1.80 ± 0.11，1.56 ± 0.07，1.42 ± 0.06，respectively. Statistically significant differences were observed among them（P = 0.000）. There was a high signifi? cantly positive correlation between ADC value and histopathological differentiation of CCRCC（r = 0.905，P = 0.000）. The ROC curve showed the optimal cutoff point of ADC value was 1.61 × 10- 3 mm2/s in diagnosing well-differentiated CCRCC. Taking 1.61 × 10-3 mm2/s as the threshold value，sensitivity and specificity of differential diagnosis was 89.5% and 99%，respectively. The ROC curve showed the optimal cutoff point of ADC value was 1.54 × 10-3 mm2/s in diagnosing poorly-differentiated CCRCC. Taking 1.54 × 10-3 mm2/s as the threshold value，sensitivity and specificity of differential di? agnosis was 86.7% and 98.8%，respectively.【Conclusion】ADC value is important for predicting histopathological differ? entiation of CCRCC .