bjective To explore clinical value of magnetic resonance (MR) diffusion weighted imaging (DWI) in the diagnosis of prostate cancer. Methods 90 cases of clinical data of patients with prostate cancer in our hospital from February 2012 to December 2014 were selected as the research samples, conventional magnetic resonance imaging (T2WI) and DWI were performed 1 month before operation,apparent diffusion coefficient values (ADC) of three diagnostic methods [T2WI, DWI, (T2WI+DWI)] were recorded,diagnosis results were compared with histopathological findings,sensitivity, specificity and accuracy of three diagnostic methods were compared,correlation between ADC values, prostate cancer Gleason grading and TNM staging were analyzed. Results ADC value of patients with early-stage prostate cancer [(0.85±0.17)×10-3mm2 /s] was slightly lower than patients with benign prostatic hyperplasia and prostatitis patients (P>0.05),with the increase of TNM stage, ADC values of prostate cancer patients was reduced, and there was no significant difference in each period (P>0.05). Diagnostic sensitivity to earlystage prostate cancer of three diagnostic methods (T2WI, DWI, T2WI+DWI) were 66.7%, 83.3%, 90.0% respectively, specificity were 76.7%, 75.0%, 80.0% respectively, accuracy were 73.3%, 77.8%, 83.3% respectively, diagnostic sensitivity of T2WI+DWI was significantly higher than T2WI (P<0.05),there was no significant difference in the specificity and accuracy of the three diagnostic methods (P>0.05),correlation analysis showed that ADC values of prostate cancer areas were negatively correlated with Gleason grading (r=-0.576, P<0.05),there was no significant correlation with TNM stage (r=- 0.234, P>0.05). Conclusion Magnetic resonance diffusion weighted imaging has a high reference value for diagnosis of prostate cancer and evaluation of clinical condition,has a value of clinic application.