Purpose: The aim of this study was to establish a more reliable method to predict pubic arch interference (PAI) before permanent prostate brachytherapy. Material and methods: We retrospectively analyzed the nuclear magnetic resonance imaging (MRI) results of forty patients with prostate cancer, who were treated with permanent implantation of I-125 seeds (permanent brachytherapy). We measured and calculated six parameters based on the MRI results: 1. The prostate volume (PV); 2. The angle of the pubic arch (AoPA); 3. The angle of PAI (AoPAI, pubic symphysis level); 4. The height of PAI (hPAI, pubic symphysis level); 5. The maximum angle of PAI (AoPAI(max)); 6. The maximum height of PAI (hPAI(max)). We then tested which parameters could accurately predict PAI through receiver operating characteristic (ROC) curve analysis. Results: The results of this study demonstrated that AoPAI, hPAI, hPAI(max), and AoPAI(max) could predict PAI. Out of forty cases in our research, 10 cases were with PAI and 30 cases without PAI during the operation. The areas under the ROC curve for PV, AoPA, AoPAI (pubic symphysis level), hPAI (pubic symphysis level), AoPAI(max), and hPAI(max)were 0.592, 0.567, 0.957, 0.940, 0.927, and 0.877, respectively. The AoPAI (pubic symphysis level), hPAI (pubic symphysis level), AoPAI(max), and hPAI(max) were statistically correlated with PAI. The boundary values were 26.32 degrees, 1.13 cm, 28.37 degrees, and 1.51 cm, respectively. Conclusions: This new method derived from MRI has predictive value, as AoPAI, hPAI, hPAI(max), and AoPAI(max) could predict PAI. Taking other factors into consideration, we suggest the use of AoPAI as a novel and very reliable predictor of PAI.