3,4-Dihydroxyacetophenone (3,4-DHAP) is one herbal extract from bald Mao-dong-qing leaves. We reported that 3,4-DHAP had anti-inflammatory function by decreasing tumor necrosis factor-α (TNF-α) secretion in macrophages. The aim of the study was to examine the effects of 3,4-DHAP on plasma and liver lipids, plasma alanine aminotranferase (ALT) and TNF-α level, vascular cell adhesion molecule-1 (VCAM-1) expression, plaque vulnerability and vascular inflammation in hypercholesterolemia-induced atherosclerotic rabbits. Male New Zealand white rabbits were randomized into negative control, positive control, 3,4-DHAP and simvastatin groups. From weeks 2 to 12, the rabbits were treated with 3,4-DHAP or simvastatin. At weeks 12, all the animals were sacrificed. Plasma lipids and ALT were measured using the enzymatic endpoint method. Plasma TNF-α was measured using enzyme-linked immuno sorbent assay (ELISA). Liver lipids concentrations were estimated using commercial kits. The expression of VCAM-1 was measured using reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. Histological analysis was used to evaluate the pathologic changes of rabbit aortas. The results showed that 3,4-DHAP markedly lowered plasma and liver lipids, lowered plasma ALT and TNF-α levels compared with the positive control group. VCAM-1 mRNA and protein were markedly inhibited by 3,4-DHAP. Decreased aortic plaque instability was evident in 3,4-DHAP-treated rabbits, as demonstrated by a thickened elastic layer, increased vascular smooth muscle cells (VSMCs) accumulation in the plaques, less neointima hyperplasia and macrophages recruitment. 3,4-DHAP may attenuate the progression of atherosclerotic lesions and stabilize plaques by lowering plasma lipids, the number of macrophages and the expression of VCAM-1, while increasing the number of VSMCs in the atherosclerotic plaques.