Objective: To establish an in vitro cell model to investigate hepatic steatosis of non-alcoholic fatty liver disease. Methods: HepG2 cells cultured in MEM containing 10; fetal bovine serum were divided into control group and model group.At 70;-80; confluency,HepG2 cells in model group were exposed to a long-chain mixture of free fatty acids (oleate and palmitate) for 24 h,cells in control group were subject to fresh medium.Lipid droplets were observed with oil red O stain and electron microscope,triglyceride and malonaldehyde were detected by respective assay kits. Results: A large number of lipid droplet were detected in model HepG2 cells;the level of triglyceride increased.However,malonaldehyde did not increase significantly compared with control group. Conclusion: Long-chain mixture of free fatty acids (oleate and palmitate) can induce steatosis in HepG2 cells,this in vitro model is simple and pragmatic for study of non-alcoholic fatty liver disease.