To mitigate the global freshwater crisis, capacitive deionization (CDI) has demonstrated its great potential for efficiently treating low-concentration saline water to produce fresh water. Nevertheless, there are still challenges in both enhancing the sodium-ion capture capability and cycling durability of cathode electrodes. Herein, we prepared a hexagonal carbon-coated Ni-Co bimetallic sulfide/g-C 3N 4 heterojunction (NCS-CN x) for application as a desalination electrode for the first time. The heterostructure effectively regulate the electronic structure and enhanced ion transport dynamics, thereby enabling superior electrochemical desalination performance. Electrochemical behaviors of NCS-CN x were explored though cyclic voltammetry, capacitance kinetics, and long-term charge/discharge testing. Desalination experiments demonstrated that the optimal NCS-CN 16 electrode delivered an extraordinary salt adsorption capacity of 57.06 mg g −1, while maintaining remarkable cyclic durability throughout a four-stage activation process over 40 cycles. The alterations in the surface chemical states of Ni/Co and the binding energy shifts of Ni–S/Co–S bonds illustrated the remarkable reversibility. Theoretical calculations elucidated the performance enhancement mechanisms via the NCS-CN x heterojunction electrode. This research provides novel perspectives on designing high-property bimetallic sulfide heterojunction electrodes for CDI application.