Arsenic pollution in water poses a significant environmental challenge due to its high toxicity and non-degradability. In this study, FeMn-layered double hydroxide (FeMn-LDH) was synthesized using hydrothermal and coprecipitation methods with different precursors for electrochemical arsenic remediation. The crystallinity of FeMn-LDH was enhanced with nitrate precursor compared to chloride precursor. The corresponding calcined layered double oxide obtained through the coprecipitation method (FMO-NO₃-Co) exhibits a significantly increased specific surface area and an optimal average pore size, facilitating efficient ion transport, and enhanced oxidation state of Mn, increasing arsenic removal efficiency. Electrochemical tests indicate that FMH-NO₃-Co exhibits relatively high specific capacitance and excellent electrochemical performance. Notably, the FMO-NO₃-Co achieves an electrosorption capacity of 55.5 mg g^-1 with 56.6 % of As(Ⅲ) being electrochemically oxidized, demonstrating superior electrocatalytic activity for the oxidation of As(Ⅲ) and high-performance electrosorption of As(V). The arsenic removal mechanism was comprehensively analyzed, revealing that Mn²⁺/Mn³⁺ redox cycling played a key role in As(Ⅲ) oxidation, while Fe-based coordination sites contributed to As(V) adsorption. Furthermore, the enhanced porosity and conductivity of the calcined LDH materials significantly improved charge transfer efficiency, thereby accelerating the arsenic removal process. Overall, this study provides valuable insights into the potential application of FeMn-LDH in electrochemical arsenic remediation.