The relationship between macrophages and the progression of abdominal aortic aneurysms (AAA) remains unclear, and effective biomarkers are lacking. In this study, we elucidate the mechanism by which macrophages promote AAA development and identify associated biomarkers, with the goal of developing new targeted therapies and improving patient outcomes. Differential expression analysis, weighted gene co-expression network analysis, and single-cell analysis were used to identify macrophage-related genes in an AAA dataset. Machine learning algorithms identified THBS1, HCLS1, DMXL2, and ZEB2 as key macrophage-related genes upregulated in AAA; these four hub genes were then used to construct a nomogram as an auxiliary tool for clinical diagnosis. Subsequent downstream single-cell and CellChat analyses were conducted to observe the interactions between macrophages and fibroblasts and analyze potential pathways. Single-cell validation confirmed enhanced THBS1 expression in macrophages within AAA. CellChat analysis revealed enhanced interaction between macrophages and fibroblasts in AAA through THBS1–CD47 signaling. Finally, clinical samples from patients with AAA confirmed the high expression of THBS1 and CD47 in AAA. Our findings highlight THBS1 as a potential driver of macrophage-mediated AAA formation and an important biomarker for AAA diagnosis.