Objective To investigate the application value of diffusion weighted imaging (DWI) and apparent diffusion coefficient (ADC) in the diagnosis of benign prostatic hyperplasia (BPH) and prostate cancer (PCA). Methods 42 cases of patients with PCA confirmed by biopsy or surgical pathology (PCA group) and 38 cases of patients with BPH confirmed by surgery and follow-up (BPH group) in our hospital from May 2011 to June 2016 were enrolled in the study. DWI was performed before operation, and the b value was 800s/mm². The DWI and ADC images of the two groups were observed and compared. The ADC values of non-PCA invading the prostate tissues and BPH tissues were compared, and ADC values of peripheral carcinoma tissues of PCA and the prostate tissues of BPH were also compared. Results In BPH group, the gland hyperplasia and muscle fiber hyperplasia showed inhomogeneous high signal and inhomogeneous low signal on DWI and ADC images. PCA group showed high signal on DWI and low signal on ADC. There were no significant differences between the two groups in ADC values of normal peripheral zone, glandular hyperplasia, interstitial hyperplasia, bladder and obturator muscle. Compared with the ADC value of PAC peripheral zone, the ADC values of the peripheral zone, the central gland hyperplasia and central muscle fiber hyperplasia of BPH group were significantly higher. Conclusion DWI and ADC can provide quantitative information for the diagnosis of prostate cancer. They are convenient and simple to use, and can be used as assistant tools for clinical diagnosis.