BACKGROUND AND AIMS: Walnut oil (WO) and peanut oil (PO) are common vegetable oils rich in unsaturated fatty acids, known to alleviate atherosclerosis (AS) and reduce the risk of cardiovascular diseases (CVD). WO contains a higher proportion of polyunsaturated fatty acids (PUFAs) compared to PO. This study aimed to explore the influence of WO on AS and elucidate its potential mechanisms, providing a theoretical basis for enhancing the application of WO in functional foods and pharmaceuticals. METHODS: AS was established in rats using a high-fat diet and vitamin D3 injections. Rats with AS were administered WO or PO via gavage at a dose of 1.2 g/kg for 4 weeks. Serum lipid levels and arterial injury were assessed, and transcriptomic and metabolomic analyses of the rat vasculature were performed. RESULTS: Both WO and PO significantly lowered serum lipid levels and the atherogenic index (AI) in rats, reducing arterial wall injury and plaque formation. WO exhibited a more pronounced effect, particularly in decreasing serum levels of TG, TC, HDLC, and LDL-C. Transcriptomic analysis indicated that fatty acid, amino acid metabolism were crucial in AS development due to a high-fat diet. Metabolomic analysis indicated significant changes in the metabolism of arginine, proline, cysteine, methionine, glycine, serine and threonine in rats treated with WO. CONCLUSION: WO and PO help alleviate AS by regulating lipid metabolism and influencing pivotal metabolic pathways like TCA cycle and cysteine-methionine metabolism. The more significant impact of WO indicates its potential as a dietary supplement for preventing and treating AS.