Objective The aim of this study was to investigate the effect and mechanism of quercetin on lipid droplet formation in foam cells induced by oxidized low-density lipoprotein (ox-LDL).Methods Mouse RAW264.7 cells were induced by 50 mg/L ox-LDL to construct a foam cell model. After different quercetin concentrations were treated for different time, the optimal quercetin concentration and time were screened by CCK8 assay. Based on the constructed foam cell model, the formation of fat droplets was observed by oil red O staining after quercetin treatment with or without AS1842856 (FOXO1 inhibitor). Apoptosis was detected by flow cytometry. The protein expression of FOXO1 in each group was detected by Western blot. Autophagosome formation was observed by acridine orange staining. The mRNA and protein expression levels of Beclin1, LC3II and P62 were detected by qRT-PCR and Western blot.Results After being treated with 100 μmol/L quercetin for 12 h, the formation of fat droplets and apoptosis of foam cells were inhibited (P<0.05). Compared with control group, there was an increase in fat droplet formation and apoptosis (P<0.05), a decrease in autophagosome (P<0.05), a decrease in FOXO1 protein expression (P<0.05), a decrease in Beclin1 and LC3II protein and mRNA expression levels (P<0.05), and the expression levels of P62 protein and mRNA were found to be increased (P<0.05) in model group. Compared with model group, quercetin treatment up-regulated FOXO1 protein expression (P<0.05), induced autophagosome formation (P<0.05), promoted the protein and mRNA expression levels of Beclin1 and LC3II (P<0.05), and inhibited the protein and mRNA expression levels of P62 (P<0.05). In addition, treatment with the FOXO1 inhibitor AS1842856 reversed quercetin’s effect on OX-LDL-induced foam cells.Conclusion Quercetin induced autophagy by upregulating FOXO1 expression and inhibited fat droplet formation induced by OX-LDL.