Abstract: To investigate the effects of histamine and Lactobacillus reuteri on Pelteobagrus fulvidraco, three isonitrogenous diets, namely diet C (control, with a 147 mg/kg content of histamine), diet H (with a 479 mg/kg content of histamine) and diet H+B (histamine+ bacteria: a 496 mg/kg content of histamine and 1×10⁵ CFU/g L. reuteri), were formulated for a 56-day trial of P. fulvidraco juveniles (14.23±0.65) g. Our data indicated that plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity were significantly lower in group H+B compared with those of group H (P<0.05), while there was no significant difference between group H+B and group C (P>0.05). Meanwhile, liver glutathione-s-transferase (GSH-ST) activity and malondialdehyde (MDA) content were dramatically reduced in group H+B compared with those of group H (P<0.05), while there was no significant difference between group H+B and group C (P>0.05). Furthermore, the HE staining showed that there were inflammatory cells infiltrating in the liver of fish fed with diet H, while no hepatocyte abnormality observed in group C and group H+B, and that the intestinal folds decreased significantly with shorter and edema in diet H group, while this is no marked difference in the length of intestinal folds between group C and H+B. Overall, our studies indicated the protective effect ofL. reuteri against histamine in cultured fish diet.