The present invention relates to bifidobacterium breve CCFM1025, its fermented food and application thereof. Bifidobacterium breve CCFM1025 of the present invention can improve the depression-like behavior of depressed mice, increase the levels of 5-hydroxytryptophan, 5-hydroxytryptophan and brain-derived neurotrophic factor in the brain of depressed mice, and reduce the levels of 5-hydroxytryptophan in the serum of depressed mice. Corticosterone levels, increased serum 5-hydroxytryptamine levels in depressed mice, improved intestinal flora disturbance in depressed mice, decreased intestinal Veillonellaceae abundance, increased the abundance of Bifidobacteria and Mycoplasmaceae , increase the α-diversity of intestinal flora, reduce the occurrence of inflammatory bowel disease and obesity; increase the mRNA level of tryptophan hydroxylase 1 in simulated enterochromaffin cells, and increase the level of 5-hydroxytryptophan in this cell Secretion, specifically providing precursors for the synthesis of 5-HT in the brain. It has broad application prospects.