The　application　of　electrokinetic-enhanced　in　situ　chemical　oxidation　remediation　of　contaminated　sediments　has　attracted　increasing　attention.　However,　the　molecular　changes　in　dissolved　organic　matter　(DOM)　during　these　remediation　processes　remain　unexplored.　To　address　the　gap,　we　explored　the　molecular　transformation　of　DOM　subjected　to　electrokinetic　(EK)-persulfate　treatment.　The　findings　revealed　that　DOM　transitioned　from　a　reduced　to　an　oxidized　state,　marked　by　the　removal　of　low　O/C　molecules　and　the　formation　of　high　O/C　molecules.　Heteroatom-containing　molecules　accumulated　and　constituted　the　dominant　fraction　among　the　resistant　molecules　post-treatment.　N-containing　and　Cl-containing　molecules　displayed　elevated　N/C　and　Cl/C　ratios　during　the　treatment,　decomposing　into　smaller　and　N-rich　or　Cl-rich　molecules,　while　S-containing　molecules　exhibited　a　decrease　in　S/O　ratios.　Oxygen　addition　reaction　and　dealkyl　group　reaction　were　identified　as　the　two　most　common　transformation　pathways,　contributing　to　the　increased　oxidation　and　resistance　of　DOM　molecules.　This　study　deepens　our　understanding　of　DOM　transformation　using　EK-persulfate　treatment　and　aids　in　assessing　the　potential　risks　associated　with　resistant　molecules　in　its　practical　application.　©　2025　Elsevier　B.V.