Objective To compare the diagnostic efficacies of ⁶⁸gallium-labelled prostate-specific membrane antigen (PSMA) ligand PSMA-11 (⁶⁸Ga-PSMA-11) positron emission tomography-computed tomography (PET-CT) and whole-body magnetic resonance imaging (WB-MRI) for detecting distant metastasis in prostate cancer patients. Methods The clinical data of 52 patients with prostate cancer who underwent ⁶⁸Ga-PSMA-11 PET-CT and WB-MRI in our hospital from Jan. to Dec. 2019 were retrospectively analyzed. The images of ⁶⁸Ga-PSMA-11 PET-CT and WB-MRI were reviewed with blinding by professional nuclear medicine physicians and radiologists, respectively, and then the patients were grouped according to the best valuable comparator (BVC). The receiver operator characteristic (ROC) curve was drawn according to the result, and the area under the curve (AUC) was calculated. The sensitivity and specificity of the two tests were statistically analyzed. Results Of the 52 patients, 20 were diagnosed without distant metastasis, 32 with distant metastasis. The AUC of WB-MRI and ⁶⁸Ga-PSMA-11 PET-CT in detecting distant metastasis were 0.844 (95% CI 0.719-0.968) and 0.959 (95% CI 0.719-0.968), respectively; the sensitivity and specificity were WB-MRI (93.75%[30/32], 75.00%[15/20]) and ⁶⁸Ga-PSMA-11 PET-CT (96.88%[31/32], 95.00%[19/20]), showing no significant differences (all P>0.05). There were 25 cases of bone metastasis and 29 cases of lymph node metastasis in patients with distant metastasis. The sensitivity and specificity in detecting bone metastasis were ⁶⁸Ga-PSMA-11 PET-CT (92.00%[23/25], 100.00%[27/27]) and WB-MRI (60.00%[15/25], 88.89%[24/27]), showing significant difference in sensitivity (P=0.04). The sensitivity and specificity of the two tests in detecting lymph node metastasis were (89.66%[26/29] vs 86.21%[25/29]) and (95.65%[22/23] vs 91.30%[21/23]), showing no significant differences (both P>0.05). Conclusion Both ⁶⁸Ga-PSMA-11 PET-CT and WB-MRI have high diagnostic efficacy for the detection of distant metastasis. ⁶⁸Ga-PSMA-11PET-CT is significantly more advantageous compared to WB-MRI for the detection of bone metastasis.