At　present,　foodborne　diseases　(FBDs)　caused　by　bacteria　are　gradually　increasing　every　year,　and　the　development　of　new　antibiotics　is　an　urgent　necessity　for　human　beings.　To　find　novel　antibacterial　compounds,　three　sponge-derived　fungal　strains　(SCSIOS02F40,　F46,　and　F49)　were　investigated.　As　a　result,　Alternaria　sp.　SCSIOS02F49　was　selected　for　investigation　on　its　secondary　metabolites　because　its　ethyl　acetate　(EtOAc)　extract　of　potato　dextrose　broth　(PDB)　culture　showed　rich　metabolites　and　strong　antibacterial　activity.　Two　new　dibenzopyrones　with　rare　sulfate　group　(1-2),　together　with　10　known　compounds　(3-12),　were　isolated　from　the　Alternaria　sp.　SCSIOS02F49.　Their　structures　were　confirmed　by　nuclear　magnetic　resonance　(NMR),　mass　spectrometry　(MS)　data,　and　comparison　with　data　from　the　relevant　literature.　Almost　all　compounds　showed　moderate　inhibitory　activity　against　eight　foodborne　bacteria　(FBB)　with　minimum　inhibitory　concentration　(MIC)　values　in　the　range　of　15.6-250　mu　g/ml,　and　minimum　bactericidal　concentration　(MBC)　values　in　the　range　of　31.3-250　mu　g/ml.　The　antibacterial　mechanism　of　compound　1　was　preliminarily　investigated　using　growth　curves,　scanning　electron　microscopy　(SEM),　and　flow　cytometry　(FCM),　which　revealed　that　compound　1　altered　the　external　structure　of　Staphylococcus　aureus　and　caused　the　rupture　or　deformation　of　the　cell　membranes.　This　research　provides　lead　compounds　for　the　development　of　new　antibiotics　or　microbial　preservatives.