Preeclampsia (PE) presents a significant challenge in pregnancy due to its high incidence and clinical fatality rate. Previous studies have emphasized the involvement of autophagy and cellular immunity in PE pathogenesis; however, research on autophagy-related genes in PE and their clinical significance is limited. This study aimed to identify autophagy-related genes with diagnostic potential for PE and investigate their correlation with immune infiltration in preeclamptic placenta. Gene expression profiles of PE were obtained from the Gene Expression Omnibus (GEO) database. LIMMA and functional enrichment analyses identified 23 differentially expressed autophagy-related genes, primarily involved in autophagy, endoplasmic reticulum stress, and apoptosis. Three autophagy-related genes (APOL1, CAPNS1, and GABARAP) were identified as biomarkers, and a nomogram model integrating these genes exhibited good predictive performance. Validation analyses confirmed consistent expression levels of the three genes. Analysis of immune cell infiltration suggested their involvement in PE pathogenesis, with potential associations between feature genes and inflammatory responses. In conclusion, autophagy feature genes were identified, and a diagnostic nomogram for PE was constructed, offering potential biomarkers for diagnosis and therapy in PE patients.