The　present　study　aims　to　investigate　the　impacts　of　a　typical　recalcitrant　organic　compound,　namely　oleic　acid,　on　the　floc　characteristics　of　activated　sludge,　including　extracellular　polymeric　substances　(EPS)　and　polyhydroxyalkanoates　(PHA)　under　different　operation　modes　of　a　sequencing　batch　reactor　(SBR).　In　addition,　the　morphological　structure,　sludge　settling　performance,　and　microbial　community　structure　were　further　compared　with　those　under　a　treatment　system　based　on　glucose　as　a　substrate.　The　results　showed　comparatively　lower　EPS　concentrations　under　the　oleic　acid-based　SBR　system　than　those　observed　under　the　glucosebased　treatment　system,　particularly　the　polysaccharides　(PS)　contents　of　EPS.　Furthermore,　the　oleic　acid　compound　resulted　in　comparatively　reduced　PHA　concentrations.　The　oleic　acid-based　SBR　system　revealed　a　better　settling　performance　than　that　of　the　glucose　control　group,　showing　maximum　sludge　volume　index　(SVI)　values　of　170　and　633　mL/g,　respectively.　Indeed,　the　oleic　acid-based　SBR　system　inhibited　the　formation　of　filamentous　sludge　bulking.　The　obtained　high-throughput　sequencing　results　demonstrated　the　reduction　effect　of　the　recalcitrant　oleic　acid　organic　compound　on　the　sludge　microbial　abundance　and　diversity.　However,　the　relative　abundance　showed　Mycobacterium　a　temporal　increase　over　the　experiment,　reaching　up　to　16.66　%　and,　consequently,　becoming　the　dominant　microbial　species.　These　findings　provide　a　theoretical　basis　for　the　addition　of　recalcitrant　biodegradable　organic　compounds　to　influents　of　actual　wastewater　treatment　plants,　outlining　the　impact　of　oleic　acid　on　sludge　floc　characteristics.