Dissolved　organic　matter　(DOM)　plays　an　important　role　in　regulating　the　fate　of　mercury　(Hg),　e.g.,　mobility,　bioavailability,　and　toxicity.　Clarifying　the　role　of　DOM　in　binding　Hg　in　the　treatment　processes　of　sewage　sludge　is　important　for　relieving　Hg　contamination　risks　in　land　applications.　However,　the　impacts　of　DOM　on　Hg　binding　in　sewage　sludge　are　still　unclear.　In　this　study,　we　investigated　the　evolution　of　Hg　and　its　speciation　in　full-scale　sludge　anaerobic　digestion　(AD)　with　thermal　hydrolysis.　The　role　of　DOM　in　binding　Hg(II)　was　further　analyzed.　The　results　showed　that　AD　with　thermal　hydrolysis　led　to　an　increase　in　the　Hg　content　in　the　sludge　(from　3.72　+/-　0.47　mg/kg　to　10.75　+/-　0.16　mg/kg)　but　a　decrease　in　Hg　mobility　(the　mercury　sulfide　fraction　increased　from　60.56　%　to　79.78　%).　Further　adsorption　experiments　revealed　that　at　equivalent　DOM　concentrations,　DOM　with　a　low　molecular　weight　(MW　＜1　kDa)　in　activated　sludge,　DOM　with　a　medium　molecular　weight　(1　kDa　5　kDa)　in　both　anaerobically　digested　sludge　and　conditioned　sludge　showed　high　binding　amounts　of　Hg　(II),　with　1372.54,　535.28,　942.09　and　801.51　mg　Hg/g　DOM,　respectively.　Parallel　factor　analysis　(PARAFAC)　and　fluorescence　quotient　(FQ)　results　showed　that　tryptophan-like　and　tyrosine-like　substances　had　high　binding　affinities　for　Hg(II).　Furthermore,　X-ray　photoelectron　spectroscopy　(XPS)　indicated　that　the　reduced　organic　sulfur　contained　in　the　DOM　was　potentially　bound　to　Hg　through　the　interactions　of　Hg　-S　and　Hg　-O.　These　results　indicated　that　DOM　may　play　special　roles　in　regulating　Hg　speciation.　The　association　between　DOM　and　Hg(II),　such　as　the　significant　positive　correlation　(　p　＜　0.05)　between　the　dissolution　rate　of　Hg(II)　and　release　of　tryptophan-like　substances　during　thermal　hydrolysis,　suggested　the　potential　way　for　removing　Hg　from　sludge.