Coal　liquefaction　wastewater　(CLW)　contains　numerous　toxic　and　biorefractory　organics.　A　series　of　advanced　treatment　processes　were　designed　to　remove　the　dissolved　organic　matter　(DOM)　from　CLW.　Here,　the　reactivity　and　state　of　the　DOM　in　the　treatment　train　were　studied　in　relation　to　its　chemical　composition　by　a　Fourier　transform　ion　cyclotron　resonance　mass　spectrometry　(FT-ICR-MS)　analysis.　Within　an　isobaric　group,　the　raw　CLW　possessed　a　high　average　double-bond　equivalent　(DBEwa)　and　low　H/C-wa　values　with　the　N-　and　S-containing　compounds　accounting　for　approximately　77%　of　the　raw　CLW,　which　represented　lignin　(73.6%)　and　condensed　aromatic　structures　(19.8%).　In　addition,　the　flotation　process　removed　some　hydrophobic　DOM　compounds　with　highly　unsaturated　states,　which　were　biorefractory　compounds.　Ozonation　and　catalytic　oxidation　processes　preferentially　removed　the　highly　unsaturated　compounds　and　produced　more　oxidized　molecules.　The　biofiltration　process　impacted　the　organics　composition　by　consuming　oxygen-rich　substances,　whereas　the　anoxic/oxic　(A/O)　process　converted　the　reactive　compounds　into　newly　formed　compounds　through　the　loss　of　hydrogen　(unsaturation)　from　the　original　compounds.　The　membrane　bioreactor　(MBR)　process　was　more　efficient　in　removing　the　N-containing　compounds　with　higher　unsaturated　states.　The　compounds　resistant　to　the　applied　CLW　treatment　processes　were　characterized　by　lower　molecular　weights　(approximately　250-350　Da),　higher　oxidation　states　(O/S　＞　6),　numerous　carboxylic　groups,　and　non-biodegradable　features.　(C)　2018　Elsevier　B.V.　All　rights　reserved.