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Introduction: To investigate the application value of diffusion-weighted imaging (DWI), the difference of apparent diffusion coefficient (ADC) value calculated from ADC map was used, in evaluating the pathologic grade of astrocytic tumors. Methods: 33 patients with histopathologically proven supratentorial astrocytic tumors were included in this prospective study. All of them received conventional magnetic resonance imaging (MRI), DWI with diffusion factor of 0 and 50 s/mm and of 0 and 3,000 s/mm, and perfusion-weighted imaging (PWI) examinations. Pseudo-color ADC maps were obtained by means of using ADC map with low b value (0 and 50 s/mm) minus ADC map with high b value (0 and 3,000 s/mm). Results: The highest ADC value of grades I-II, grade III, and grade IV was (0.91 ± 0.07) × 10, (1.81 ± 0.38) × 10, and (2.36 ± 0.32) × 10 mm/s, respectively, and there was statistical difference among them ( p < 0.001). The highest ADC value between low-grade (grades I-II) and high-grade (grades III-IV) astrocytic tumors showed statistical difference as well ( p < 0.001). The highest ADC value of astrocytic tumors correlated positively with the pathologic grade of tumor ( r = 0.853, p < 0.001). Positive correlation was found between the highest ADC value and maximum relative cerebral blood volume (rCBV) value ( r = 0.829, p < 0.001) in high-grade astrocytic tumors; however, the highest ADC value and maximum rCBV value had no significant correlation in low-grade astrocytic tumors ( r = 0.259, p = 0.536). Conclusion: Quantitative analysis of highest ADC value of supratentorial astrocytic tumors may provide valuable information of tumor microcirculation and perfusion, thus allowing a promising new method for preoperatively assessing the pathologic grade of tumor. [ABSTRACT FROM AUTHOR]