Objective:To compare the performance of 68Ga-prostate specific membrane antigen (PSMA) PET/CT and MRI in preoperative diagnosis and staging of primary prostate cancer. Methods:Twenty-four patients with prostate cancer, who underwent preoperative 68Ga-PSMA PET/CT and prostate MRI in Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology between April 2018 and December 2019, were retrospectively enrolled. The pathological and follow-up results were considered as the gold standard, and diagnostic efficiencies of the 2 imaging methods were compared per patient and per type of lesions (seminal vesicle invasion, bladder neck invasion, lymph node metastasis and bone metastasis). The χ2 test was used for data analysis. Results:Prostate cancer was confirmed by pathology in 24 patients, including 6 cases with both seminal vesicle and bladder neck invasion, 5 cases with seminal vesicle invasion and 3 cases with invasion of bladder neck. Gleason scores in patients were as follow: 7 in 9 patients, 8-9 in 15 patients. The detection rates of 68Ga-PSMA PET/CT and MRI for primary prostate cancer were both 100%(24/24). The sensitivity, specificity and accuracy of 68Ga-PSMA PET/CT and MRI for detecting seminal vesicle invasion were 10/11, 13/13, 95.8%(23/24) and 9/11, 11/13, 83.3%(20/24), respectively. The specificity and accuracy were significantly different ( χ2 values: 6.231, 13.470, both P<0.05). The sensitivity, specificity and accuracy of 68Ga-PSMA PET/CT and MRI for detecting bladder invasion, which were 7/9, 13/15, 83.3%(20/24) and 3/9, 14/15, 70.8%(17/24), respectively, were not significantly different( χ2 values: 1.285, 0.164, 2.880, all P>0.05). Furthermore, the sensitivity, specificity and accuracy of 68Ga-PSMA PET/CT for detecting pelvic lymph node metastasis were 11/11, 13/13 and 100%(24/24), respectively, and those of MRI for evaluating pelvic lymph node metastasis were 6/11, 11/13 and 70.8%(17/24), and the specificity of the 2 methods were significantly different ( χ2=6.231, P<0.05). All the 5 patients with pelvic bone metastasis were positive on 68Ga-PSMA PET/CT imaging, but only 2 of them were positive on MRI. Information from 68Ga-PSMA PET/CT changed pelvic TNM stage in 41.7%(10/24) patients who underwent MRI for initial staging. Conclusions:68Ga-PSMA PET/CT imaging and MRI can both accurately detect intermediate- to high-risk primary prostate cancer and seminal vesicle invasion. 68Ga-PSMA PET/CT imaging is superior to MRI for evaluating lymph nodes and bone metastasis. 68Ga-PSMA PET/CT provides high accuracy for preoperative diagnosing and staging intermediate- to high-risk prostate cancer.