Objective: To analyze the risk factors for postoperative pathological upgrade of prostate cancer patients with single core positive biopsy, and to attempt to build a mathematical model for predicting postoperative pathological upgrade in these cancer patients with single core positive biopsy. Methods: A retrospective analysis was conducted on 1 349 patients diagnosed with prostate cancer and undergoing radical prostatectomy at Peking University First Hospital from January 2015 to August 2020. The patients' age, body mass index, clinical stage, prostate imaging reporting and data system (PI-RADS) scores, prostate volume in magnetic resonance imaging (MRI), Gleason score of biopsy, serum prostate specific antigen (PSA) before biopsy and operation, surgical method and pathological stage were inclu-ded in the analysis. The variables with P < 0.1 in univariate analysis were included to construct multi-variate Logistic regression and the nomogram was drawn. The model was evaluated using the receiver operating curve. Results: A total of 71 patients were included in this research, with 34 patients in the upgraded group and 37 patients in the non-upgraded group. There were no significant differences in the patients' age (P=0.585), body mass index (P=0.165), operation method (P=0.08), prostate volume in MRI (P=0.067), clinical stage (P=0.678), PI-RADS score (P=0.203), difference of PSA density (P=0.063), Gleason score in biopsy (P=0.068), PSA before puncture (P=0.359) and operation (P= 0.739) between the two groups. However, there were significant differences in the proportion of tumor tissue (P=0.007), postoperative pathological stage (P < 0.001) and postoperative Gleason score (P < 0.001) between the two groups. The preoperative variables with a P value of less than 0.1 (prostate volume in MRI, difference of PSA density, proportion of tumor tissue and Gleason score in biopsy) in univariate analysis were included in the Logistic regression, and the nomogram was drawn. Only the prostate volume in MRI had a P value of less than 0.05. The area under the curve of the model was 0.773. Conclusion: In patients with single core positive biopsy, if the prostate volume is small or the proportion of tumor in positive core is small, clinicians should be alert to the possibility of postoperative pathology upgrading, preoperative risk stratification should be carefully considered for patients with possible pathological upgrading. This model can be used to predict the pathological upgrade of patients with single core positive biopsy.