Anaerobic　digestion　of　waste　activated　sludge　(WAS)　has　always　been　restricted　by　the　low　rate　of　sludge　hydrolysis,　due　to　the　complex　substrates　structured　by　cell　walls,　intracellular　constituents　and　extracellular　polymeric　substances　(EPS),　leading　to　a　long　retention　time　and　a　low　methane　output.　This　study　reported　a　novel　ultrasonic　(US)-enhanced　percarbonate　oxidation　to　improve　anaerobic　WAS　digestion.　Results　showed　that　US　enhanced　sodium　percarbonate　(SPC)　oxidation　and　reduced　the　SPC　dosage　required　for　WAS　disintegration　as　compared　to　sole　SPC　groups,　with　the　cumulative　methane　yield　being　enhanced　by　46.8　%　after　the　optimal　pretreatment,　i.e.,　US　+　0.15　g　SPC/g　TSS.　Kinetic　analysis　demonstrated　that　US-enhanced　SPC　pretreatment　boosted　both　the　hydrolysis　rate　and　biochemical　methane　potential　of　anaerobic　WAS　digestion,　simultaneously.　Mechanistic　explorations　revealed　that　US-enhanced　SPC　significantly　promoted　substrates　solubilization,　hydrolysis　and　acidification　during　the　pretreatment　stage,　providing　huge　amounts　of　reaction　intermediates　directly　available　for　subsequent　methanation.　Meanwhile,　US-enhanced　SPC　improved　biodegradability　of　soluble　substrates,　reduced　particle　size　and　increased　specific　surface　area　of　WAS,　which　created　preferable　conditions　for　anaerobic　biotransformation.　Further　analysis　suggested　that　US-enhanced　SPC　boosted　the　metabolic　activity　associated　with　key　bioprocesses　in　digestion　system,　in　accord　with　enhanced　methane　production.　Likewise,　microbial　community　analysis　illustrated　the　functional　microbes　(e.g.,　Romboutsia　sp.)　participating　in　key　bioprocesses　were　enriched　by　US-enhanced　SPC　pretreatment,　with　their　total　abundances　increasing　from　13.3　%　to　23.1　%.　©　2022　Elsevier　B.V.