Abstract: Aiming at the problem of restricting the subsequent disposal of dredged sediment with high water content, Fe²⁺-perdisulfate (PDS) conditioning - horizontal electro-dewatering (HED) process was used to treat sediment samples. The operating parameters (Fe²⁺ and PDS dosage, voltage, power-on time) of Fe²⁺-PDS conditioning - HED process were optimized through the response surface method (RSM), and the variations in the morphology and properties of the sediment at the conditioning stage, as well as the changes in the water content and organic components of the sediment at various stages of the process (conditioning, gravity settling, HED) were analyzed. The results showed as follows: 1) The optimal dosage of Fe²⁺ and PDS for the conditioning stage was 4 mg/g (TSS) and 10 mg/g (TSS), respectively. The optimal power-on time and voltage of the HED stage were 80 min and 45 V, respectively. Under the above parameters, the water content of dredged sediment decreased from 88.55% to 55.15%. 2) At the conditioning stage, the bound water content of sediment decreased from 0.44 g/g (DS) to 0.28 g/g, the total amounts of proteins and polysaccharides in extracellular polymeric substances (EPS) increased, while the fluorescence intensity of protein-like substances and soluble microbial byproduct-like materials (SMBP) in Slime layer decreased. The total fluorescence intensity in the tightly bound EPS (TB-EPS) increased to 12.40×10⁷ AU·nm². At the HED stage, the effect of electric field led to further release of the organic matters in the sediment around the cathode region, and the fluorescence intensity of SMBP in each layer of EPS around the cathode region increased significantly. 3) SO₄ ⁻· produced at the conditioning stage could oxidize and crack the microbial cells in the sediment and release the intracellular contents into EPS, and the simultaneous changes in water distribution and EPS components of the sediment occurred. Fe(Ⅲ) produced in situ altered the floc structure of the sediment through coagulation, thus contributing to the improvement of the dewatering performance of the sediment. The research showed that Fe²⁺-PDS conditioning-HED process could effectively reduce the water content of the dredged sediment, so as to provide technical support for the treatment of dredged sediment.