Abstract: Objective: To evaluate the diagnostic value of combining biparametric magnetic resonance imaging quantitative indicators (ADC value and T2 mapping value) with prostate-specific antigen density (PSAD) for differentiating prostate lesions with PI-RADS 3-4 scores, thereby optimizing precision stratification and management of prostate cancer (PCa). Methods: A retrospective analysis was conducted on 91 patients with prostate lesions diagnosed as PI-RADS 3-4 scores (43 PCa cases, 48 non-PCa cases) confirmed by prostate pathology. MRI-derived parameters (ADC value, T2 mapping value) and PSAD data were also collected. Receiver operating characteristic (ROC) curves were used in order to assess the diagnostic performance of individual parameters. A logistic regression model was constructed for the combined diagnostic approach (PSAD-ADC-T2 mapping), and its performance was compared with that of traditional PI-RADS scoring systems. Results: Single-parameter analyses showed that the diagnostic efficacy AUCs of ADC, T2 mapping, and PSAD for PCa were 0.834, 0.865, and 0.776, respectively (P < 0.01). The AUC of the combined model was 0.899 (95% CI: 0.837-0.961), which was significantly higher than that of the PSAD index (P = 0.009). The sensitivity and specificity were 87.5% and 79.1%, respectively. The diagnostic gain of the combined model was particularly significant in the PI-RADS 3 subgroup. The specificity increased to 84%, and compared to the Prostate Imaging - Reporting and Data System (PI-RADS) scoring system, the rate of over - biopsy decreased by8.7%. Conclusion: The integration of the biparametric MRI quantitative indicators with PSAD significantly enhanced the diagnostic accuracy of PI-RADS 3-4 prostate lesions, providing a precise and reproducible imaging-clinical fusion tool for prostate cancer risk stratification. This approach reduces unnecessary biopsy procedures and streamlines clinical decision making, thus offering a promising strategy for optimizing patient management.