Objective To compare the diagnostic efficacy of 68Ga-PSMA-617 PET/CT and multiparameter MRI in the diagnosis of primary tumors of newly diagnosed prostate cancer.and analyze the correlation between SUVmax and clinical parameters of prostate cancer.Methods A retrospective analysis of the clinical data of 104 patients with newly diagnosed prostate cancer who underwent 68Ga-PSMA-617 PET/CT and multi-parametric MRI from June 2017 to April 2018.The final pathological results were used as the gold standard for diagnosis.The age ranged from 42 to 89 years,with an average of (70.4 ± 8.9) years.The median total serum PSA was 18.44 (8.71,48.01)ng/ml.The pathological results were positive in 68 cases and negative in 36 cases.The sensitivity,specificity was calculated,the ROC curve was drawn and AUC value was calculated.The relationship between SUVmax value of prostate cancer and clinical parameters was analyzed.Results The sensitivity of 68Ga-PSMA-617 PET/CT was 95.59％ (65/68) and the specificity was 88.89％ (32/36);the sensitivity of MRI examination was 91.18％ (62/68) and the specificity was 63.89％ (23/36).There were statistical differences between the specificity of the two examination (P =0.012).The ROC curve of 68 Ga-PSMA-617 PET/CT was plotted and the AUC value was 0.954.Among the 104 suspected prostate cancer patients,the median SUVmax of benign prostatic tissue was 3.20(2.83,3.70),and the median SUVmax of prostate cancer tissue was 12.21 (7.48,17.46).Among 68 patients with prostate cancer,there were statistical differences between SUVmax values of prostate cancer tissues with different Gleason scores (P ＜ 0.01),ISUP group (P ＜ 0.01),risk grades (P =0.021),and SUVmax values.There was a positive correlation with Gleason score and ISUP group (r1 =0.7420,P＜0.01;r2 =0.754,P＜0.01).Conclusions The 68Ga-PSMA-617 PET/CT examination had higher diagnostic efficacy than the multiparametric MRI for prostate cancer.The higher the SUVmax value predict the higher grade and higher risk.