Probiotic dietary supplementation has been widely used and has positive effects on the growth performance and host health of different fish species. Little attention is paid to its influence on fish gastrointestinal mucosal microbiota. A feeding trial was conducted to investigate the potential effects of probiotic compounds of on the growth performance and gastric and intestinal mucosal microbiota of rainbow trout. A total of 360 rainbow trout with average body weight of (205.1±4.82) g were distributed in four equal groups in three replicates, and received one of the following experimental diets for 42 days:basal diet, basal diet supplemented with 5×10⁶/5×10⁷ CFU/g (T1, see tables 1 and 2), 1.5×10⁷/1.5×10⁸ CFU/g (T3, see tables 1 and 2), and 2.5×10⁷/2.5×10⁸ CFU/g (T5, see tables 1 and 2) of probiotic compounds. Significant improvement in weight gain ratio, feed conversion ratio, and the specific growth rate (SGR) was found in T1 diet supplemented with probiotic compounds. Significantly decreased mortality was found in T1 and T3 diets. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was applied to compare the gastrointestinal mucosal microbiota of different treatments. In gastric mucosa, 35.7±17.0 (C0), 37.0±3.5 (T1), 36.7±13.6 (T3), and 26.0±13.2 (T5) bands were found, with no significant differences (=0.692). In intestinal mucosa, 23.3±5.8 (C0), 22.3±3.2 (T1), 16.7±8.0 (T3), and 24.7±7.4 (T5) bands were found, also with no significant differences (=0.475). The bacterial diversity of gastric mucosa increased with increasing probiotic concentration, but it decreased in T5. However, the bacterial diversity of intestinal mucosa decreased with increasing probiotic concentration, which showed recovery in T5. Using both the unweighted pair-group method with arithmetic means (UPGMA) clustering and principal component analysis (PCA) ordination, we found that the microbial community structures of gastric mucosa and intestinal mucosa were different. No significant influences were found on bacterial diversity and microbial community structure of intestinal mucosa of rainbow trout with addition of probiotic compounds of . The potential risks of high concentrations of probiotics should be paid more attention.