This study investigated the clinical role of HOTAIR in patients with carotid artery stenosis (CAS) and its mechanism in vascular smooth muscle cells (VSMCs). Patients with CAS were collected. The expression of HOTAIR was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The clinical importance of HOTAIR was revealed by the receiver operating characteristic curve. Overexpression and knockdown of HOTAIR were achieved by transfecting pCDNA3.1-HOTAIR plasmid and si-HOTAIR respectively. CCK-8 assay or Transwell assay were used to analyze the changes in cell viability or migration after transfection treatments. Double luciferase reporter gene assay confirmed the targeted relationship between HOTAIR and miR-148b-3p. The levels of miR-148b-3p in VSMCs and patients were detected by qRT-PCR. Pearson analysis was used to analyze the relationship between HOTAIR and miR-148b-3p in patients with CAS. The expression of HOTAIR in patients with CAS was significantly higher than that in healthy individuals. HOTAIR appeared to discriminate CAS patients from healthy people. The overexpression of HOTAIR increased the viability and migration of VSMCs. Silenced HOTAIR restricted the abnormal viability and migration of VSMCs. A double luciferase reporter revealed a region of complementary binding between HOTAIR and miR-148b-3p. The expression of miR-148b-3p in VSMCs was regulated by the levels of HOTAIR. Reduction of miR-148b-3p expression was substantiated in CAS patients. Pearson analysis exhibited that the expression of HOTAIR was negatively relative to the levels of miR-148b-3p. The long noncoding RNA HOTAIR might be a diagnostic biomarker for CAS patients, and it was involved in the activity of vascular smooth muscle cells.