OBJECTIVE To investigate the mechanism by which aloin （ALO） ameliorates atherosclerosis （AS）. METHODS Eight C57BL/6J mice were assigned to the control group （CON group） and fed a standard diet； thirty-two apolipoprotein E-knockout （APOE－/－） mice were randomly divided into model group （MOD group）， ALO low-dose and high-dose groups [ALO-L group， ALO-H group， 20， 40 mg/（kg·d）]， and atorvastatin positive control group [ATO group， 4 mg/（kg·d）]， with 8 mice in each group， establishing the AS model through feeding with a high-fat diet. The mice were administered the drug via gavage or given an equal volume of deionized water for 8 consecutive weeks. The lipid levels in the serum of mice were measured， and the pathological structural changes in their aortas were observed. The expressions of macrophage polarization markers （CD86+ ， CD206+） in the aorta were determined， along with the mRNA expressions of inducible nitric oxide synthase （iNOS）， tumor necrosis factor-α （TNF-α）， arginase-1 （Arg-1）， and interleukin-10 （IL-10）， as well as the protein expressions of iNOS and Arg- 1， and the phosphorylation levels of nuclear factor κB p65 （NF-κB p65） and signal transduction and activator of transcription 3 （STAT3） proteins. Additionally， a macrophage polarization model was established using lipopolysaccharide （LPS）-induced RAW264.7 cells， and the effect of ALO （400 μmol/L） on the cellular polarization phenotype was investigated. RESULTS Compared with the MOD group， administration groups all showed significant improvement in dyslipidemia （except for high-density lipoprotein cholesterol in the serum of ALO-L group） （P＜0.05）； aortic intimal structure improved significantly， plaque area was reduced significantly （P＜0.01）； the CD86+ relative fluorescence intensity in the aorta decreased significantly， the CD206+relative fluorescence intensity increased significantly （P＜0.01）， while the expressions of iNOS and TNF-α mRNA were down-regulated significantly （P＜0.05）； mRNA expressions of Arg-1 and IL-10， and protein expression of Arg-1 were increased significantly in ALO-H group and ATO group （P＜0.05）； the protein expressions of iNOS， and the phosphorylation levels of NF-κB p65 and STAT3 protein were decreased significantly （P＜0.05）. In vitro experiments further confirmed that ALO significantly reduced the proportion of LPS-induced M1-type macrophages but increased the proportion of M2-type macrophages （P＜0.01）. CONCLUSIONS ALO inhibits M1-type macrophage polarization and promotes M2-type polarization， ameliorates dyslipidemia and reduces arterial plaque formation in AS model mice， improve the structure of the aortic intima potentially through suppression of the NF-κB/STAT3 signaling pathway.