In this work, we present a study on the atomic details and the electronic structure of the NiCo2S4/KOH electrolyte interface via first-principles calculation. Both Ni-terminated and CoS2-terminated NiCo2S4 (001) surfaces are studied in order to understand the electronic structure of the interface and surface reactivity. The surface free energy indicates that the Ni-capped NiCo2S4 (001) surface is more stable than the CoS2-capped one. Upon adsorption, KOH received more electrons (0.1e) from the latter surface than from the former and the planar average differential charge density indicates that a larger electric dipole forms in CoS2-terminated NiCo2S4/KOH interface. These analyses prove that the CoS2-terminated NiCo2S4 (001) surface presents a stronger affinity for OH− in the electrolyte, which leads to the enhanced electrochemical performance. These results will not only contribute to a better understanding of the fundamental knowledge of the NiCo2S4/KOH electrolyte interface, but also provide a guidance as to enhance the electrochemical activity of NiCo2S4 materials, which will benefit the ultimate application of NiCo2S4 (001) as electrode material for electrochemical energy storage.