Background and Aims Big data gene chip analysis showed that the expression of miR-27b-3p is significantly up-regulated in abdominal aortic aneurysm (AAA) tissue and patients' serum. However, the function and action mechanism of miR-27b-3p in aortic vascular smooth muscle cells (VSMCs) remains unclear. Therefore, this study was conducted to investigate the function of miR-27b-3p in VSMCs, as well as its effects on macrophages and the extracellular matrix, and the action mechanism.Methods In VSMCs after transfection with miR-27b-3p inhibitor, the cell proliferation activity was detected by CCK-8, and the apoptosis was detected by flow cytometry. In mononuclear macrophage cell line, THP-1 cells after transfection with miR-27b-3p inhibitor, the expressions of inflammatory-associated factors were detected by ELISA, and the expression levels of matrix-related proteins were detected by Western blot. The targeting relationship between miR-27b-3p and PTEN was verified by dual luciferase reporter gene assay and related functional experiments.Results In VSMCs after miR-27b-3p knockdown, the proliferative ability was significantly increased, while the apoptotic rate was significantly decreased (both P<0.05). In THP-1 cells after miR-27b-3p knockdown, the expression levels of pro-inflammatory factors (TNF-α, IL-12) and the matrix metalloproteinase 9 (MMP-9) were significantly decreased, while the expression levels of inflammatory factors (IL-4, IL-10) and metalloproteinase inhibitor 1 (TIMP-1) were significantly increased (all P<0.05). Dual-luciferase experiments confirmed that PTEN was a target gene of miR-27b-3p. The expression level of PTEN protein was significantly down-regulated in VSMCs with miR-27b-3p overexpression, while the proliferation was significantly enhanced and the apoptotic rate was significantly decreased in VSMCs with PTEN overexpression (all P<0.05). The expression levels of TNF-α and IL-12 as well as MMP-9 protein were significantly down-regulated, while the levels of IL-4 and IL-10 as well as TIMP-1 protein were significantly up-regulated in THP-1 cells with PTEN overexpression (all P<0.05). In VSMCs and THP-1 cells with simultaneous miR-27b-3p and PTEN expression, the changes in the above variables showed no significant differences from those in the control group (all P>0.05).Conclusion miR-27b-3p can participate in regulating VSMCs cell proliferation and apoptosis through targeting PTEN, and thereby inhibit the inflammatory response and extracellular matrix protein expression of the mononuclear macrophage cells. The miR-27b-3p/TPEN molecular axis may play an important role in the occurrence and development of AAA.