Objective：To investigate the changes in serum levels of procollagen type Ⅲ（PCⅢ） and N-terminal peptide of PCIII （PII－INP） and their association with renal fibrosis in patients with obstructive nephropathy. Methods：A total of 78 patients with obstruc－tive nephropathy who were treated in our hospital from January 2012 to December 2017 and 30 individuals who underwent physical examination were enrolled. Radioimmunoassay was used to measure the serum levels of PCⅢ and PⅢNP. Renal tissue samples were collected for HE and Masson staining. The degrees of renal fibrosis were observed under a light microscope. The Spearman analysis was used to investigate the association of PCⅢ and PⅢNP with renal fibrosis. A logistic regression model was used to analyze the risk factors for renal fibrosis based on the levels of PCⅢ and PⅢNP. The receiver operating characteristic（ROC） curve was used to predict the sensitivity and specificity of PCⅢ and PⅢNP in the diagnosis of degree Ⅱ renal fibrosis. Results：The levels of PCⅢ and PⅢNP gradually increased with the increase in the degree of renal fibrosis（P<0.01）. The levels of PCⅢ and PⅢNP were positively correlated with the degree of renal fibrosis（rs=0.820 and 0.806，P=0.000 and 0.000）. PCⅢ had a sensitivity of 95.45%，a specificity of 83.93%，and an area under the ROC curve（AUC） of 0.96（95%CI=0.890 to 0.991） in predicting degreeⅡ renal fibrosis；PⅢNP had a sensitivity of 86.36%，a specificity of 92.86%，and an area under the ROC curve（AUC） of 0.93（95%CI=0.849 to 0.976） in pre－dicting degreeⅡ renal fibrosis；both of them had a high predictive value. PCⅢ（OR=1.151，95%CI=1.035 to 1.280，P=0.009） and PⅢNP（OR=1.198，95%CI＝1.039 to 1.380，P=0.013） were risk factors for renal fibrosis. Conclusion：The serum levels of PCⅢ and PⅢNP are positively correlated with the degree of renal fibrosis，and both of them have a good value in predicting severe renal fibrosis and thus hold promise for clinical application.