Objective: To investigate the correlations between serum cystatin C level and estimated glomerular filtration rate (eGFR) in patients with early diabetic nephropathy. Methods: 60 patients with early diabetic nephropathy were divided into group A (n=33) and group B (n=27) according to serum cystatin C level; 70 health examination people in our hospital during the same period were selected as group C. The serum cystatin C level, serum creatinine of all the subjects were detected and the eGFR was calculated using MDRD formula. Linear correlation analysis was used to analyze the correlations between serum cystatin C level and eGFR in patients with early diabetic nephropathy. Results: The serum cystatin C level of early diabetic nephropathy patients in group A and group B were all significantly higher than group C, while the eGFR were significantly lower (P<0.05). The serum cystatin C level of early diabetic nephropathy patients was negatively correlated with eGFR (r=-0.7193, P<0.05). Conclusions: The serum cystatin C level is negatively correlated with eGFR in patients with early diabetic nephropathy, which may be a predictor of early diagnosis of diabetic nephropathy.