Objective To investigate the effects of niacin on the lipid metabolism in rat model of non- alcoholic fatty liver disease( NAFLD). Methods Forty Sprague- Dawley rats were randomly divided into control group,model group,intervention group 1( 0. 5%niacin),and intervention group 2( 1% niacin). Rats were fed with high- fat diet for 8 weeks to induce an NAFLD model. The serum levels of alanine aminotransferase( ALT) and aspartate aminotransferase,levels of total cholesterol( TC),triglyceride,and free fatty acid in serum and liver tissue,and level of malondialdehyde( MDA) in liver tissue were measured using assay kits. The morphological and histopathological changes in the liver were observed under a microscope. Comparison of data between groups was made by univariate analysis of variance using SPSS software; moreover,least significant difference test( equal variance assumed) and Tamhane's T2 test( equal variance not assumed) were used for pairwise comparison. Results Compared with the model group,every intervention group had significantly lower levels of ALT,TC,AST,TG,and FFA( all P < 0. 05) in serum and level of MDA in liver tissue( P < 0. 05),and had significantly increased expression of PPARα mRNA( P < 0. 05),DGAT2 mRNA( P < 0. 05),and SREBP1 c mRNA( P < 0. 05). Intervention group 2had significantly reduced expression of DGAT2 mRNA and SREBP1 c mRNA compared with intervention group 1( P < 0. 05). Compared with the model group,the intervention groups had relieved fatty degeneration of hepatocytes and alleviated inflammatory cell infiltration in the centrilobular portion of the liver. Conclusion Niacin regulates lipid metabolism in NAFLD animal models,reduces lipid oxidative stress,and significantly reduces liver steatosis and fibrosis by regulating the expression of PPARα mRNA,DGAT2 mRNA,and SREBP1 c mRNA,so as to realize the protective effect against NAFLD.