Abstract: Objective To explore the influence of nano-Fe₃O₄ on short-chain fatty acids in intestinal tract of Sprague-Dawley(SD) rats.Methods Sixty SD rats(half male,half female) were randomly divided into 3 groups:5% cellulose sodium control group,low- and high-dose groups with oral gavage of nanoparticle for 4 weeks.The fresh feces samples of the rats were collected periodically and short-chain fatty acids in the samples were determined with gas chromatography.Results Compared with those of the control group,the concentration of butyric acid for the female rats decreased significantly in low- and high-dose groups (0.05±0.02 and 0.06±0.03 μg/μL)(P < 0.05);the concentration of acetic acid in the male rats of low- and high-dose groups decreased significantly (1.31±0.16 and 1.54±0.22 μg/μl)(P < 0.05);and the concentration of butyric acid (0.04±0.02 μg/μl) in the male rats of high-dose group decreased significantly (P < 0.05) by the end of the treatments.The results of pathological observation revealed vacuoles degeneration in intestinal epithelial cells,loose arrangement in goblet cells,and the number of absorptive cells decreased in the colon of rats in exposed group.Conclusion The results suggeste that nano-Fe₃O₄ may affect short-chain fatty acids in intestinal tract of SD rats.