Inhibiting　the　growth　of　spoilage　bacteria,　such　as　Pseudomonas　spp.,　is　key　to　reducing　spoilage　in　fish.　The　mucus　adhesion　test　in　vitro　showed　that　the　adhesion　ability　of　Bacillus　subtilis　was　positively　correlated　with　its　inhibition　ability　to　Pseudomonas　spp.　In　vivo　experiments　of　tilapia　showed　that　dietary　supplementation　with　B.　subtilis　could　reduce　the　adhesion　and　colonization　of　Pseudomonas　spp.　in　fish　intestines　and　flesh,　as　well　as　reduce　total　volatile　basic　nitrogen　(TVB-N)　production.　High　throughput　and　metabolomic　analysis　showed　treatment　with　B.　subtilis,　especially　C6,　reduced　the　growth　of　Pseudomonas　spp.,　Aeromonas　spp.,　Fusobacterium　spp.,　and　Enterobacterium　spp.,　as　well　as　aromatic　spoilage　compounds　associated　with　these　bacteria,　such　as　indole,　2,4-bis(1,1-dimethylethyl)-phenol,　3-methyl-1-butanol,　phenol,　and　1-octen-3-ol.　Our　work　showed　that　B.　subtilis　could　improve　the　flavor　of　fish　by　changing　the　intestinal　flora　of　fish,　and　it　shows　great　promise　as　a　microecological　preservative.