Diabetic nephropathy (DKD) is a common complication of diabetic patients, which seriously affects their quality of life and longevity. In recent years, autophagy has been found to play an important role in the pathogenesis of DKD. The aim of this study is to identify markers of autophagy associated with diabetic nephropathy, with special attention to the structural and biological role of PTGER1 protein and its role in immune infiltration. The DKD differential genes were identified by means of various sexually expressed genes (DEGs) analysis, and functional enrichment (GO) and pathway enrichment (KEGG) analysis were performed for the significant differential genes combined with weighted gene co-expression network analysis (WGCNA). Meanwhile, gene collection enrichment analysis (GSEA) was used to further explore the function of autophagy related genes. By constructing protein-protein interaction network (PPI) and GeneMania analysis, PTGER1 was identified as a key hub gene. The diagnostic value of biomarkers was evaluated by ROC curve, and the infiltration of different immune cells was analyzed. The results showed that PTGER1 was significantly up-regulated in the renal tissues of diabetic nephropathy patients. WGCNA and functional enrichment analysis revealed a close correlation between PTGER1-related autophagy pathways and immune responses. The constructed PPI network indicated that PTGER1 had significant interactions with multiple autophagy and inflammation-related proteins, and ROC curve analysis indicated the potential application value of PTGER1 in the early screening of DKD.