PURPOSE: To determine the associations among diabetes status, Metformin administration and prostate cancer (PCa) detection at biopsy in Chinese population. METHODS: A case-control study was conducted among a prospectively enrolled prostate biopsy cohort of 518 patients from Jan 2013 to Dec 2014 at our institute. Diabetes status and Metformin administration were determined through medical records and self-report. Different clinical characteristics were registered and compared among different groups. Univariate and multivariate logistic regression analyses were performed to evaluate the effects of diabetes status and Metformin administration on the detection of overall as well as high-grade PCa at biopsy. RESULTS: PCa was detected in 229 (44.2%) men, and high-grade PCa (Gleason score ≥8) was detected in 65 (12.5%) men. Diabetes was observed in 96 men, and 28 of them were administered with Metformin. Both overall and high-grade cancer detection rates were significantly higher in diabetic patients (p<0.001). In multivariate analysis, diabetes status was a risk factor for high-grade cancer detection (OR 7.699, 95%CI 3.483-17.020, p<0.001), but not for total PCa detection (OR 1.774, 95%CI 0.831-3.787, p=0.138). Meanwhile, Metformin administration was proved to be a protective factor for high-grade disease (OR 0.420, 95%CI 0.201-0.879, p=0.021) in multivariate analysis, while no correlation was detected with overall cancer detection (OR 0.786, 95%CI 0.172-3.593, p=0.756). CONCLUSIONS: Diabetes status was positively associated with biopsy-mediated high-grade PCa detection in Chinese population, while the positive association would be partly compromised by Metformin administration.