Objective To analyze and compare the diagnostic value of high-field MRI plain scan and multiple sets of b-value DWI in prostate cancer. Methods The clinical data of 50 cases of prostate cancer and 50 cases of benign prostatitis from May 2012 to May 2017 were retrospectively selected. All the patients were treated with high-field MRI plain scan and DWI scan, and the DWI scan was performed with transverse axial plane echo imaging (ERPI) sequence, and the diffusion sensitivity coefficient (b) was chosen to be a high value of 1000, 2000, 3000 s/mm2 . The efficacy of high-field MRI scan and different b-value DWI in differential diagnosis of prostate cancer and benign lesions was analyzed. Results High-field MRI scan showed that prostate cancer lesions could be located in the peripheral zone and the central glands with irregular lesions, unclear border and most breakthrough capsule, showing the surrounding tissue and bone metastases. And the sensitivity was 76.00%, the specificity was 71.70% and the accuracy was 72.00% in the diagnosis of prostate cancer. When b=1000s/mm2 , the lesion showed a slightly higher signal on the DWI map. And with the increase of b value(2000, 3000s/mm2 ), the low signal of the lesion area was more obvious than that of the normal tissue, and the metastatic lymph node and the bone metastatic lesions were shown diffuse high signal in DWI images while the benign lesions were shown not high signal and unclear display even in the higher b value. When b=1000, 2000, 3000 s/mm2 , the sensitivity of DWI in diagnosing prostate cancer was 80.67%, 89.80%, 94.00%, and the specificity was 64.52%, 73.77%, 94.00% and the accuracy was 79.00%, 88.00% and 94.00%. That is, the higher the b-value, the higher the diagnostic efficacy of DWI for prostate cancer. Conclusion Compared with the high field MRI plain scan, the application of multiple sets of b-value DWI technology has a higher diagnostic efficacy of prostate cancer and contributes to the early diagnosis and clinical treatment of prostate cancer.