In this study, density functional theory and hybrid functional theory are used to calculate the work function and energy band structure of MoS₂ and WSe₂, as well as the binding energy, work function, energy band structure, density of states, charge density difference, energy band alignment, Bader charge, and H adsorption free energy of MoS₂/WSe₂. The difference in work function led to the formation of a built-in electric field from WSe₂ to MoS₂, and the energy band alignment indicated that the redox reactions were located on the MoS₂ and WSe₂ semiconductors, respectively. The binding energy of MoS₂ and WSe₂ indicated that the thermodynamic properties of the heterogeneous structure were stable. MoS₂ and WSe₂ gathered electrons and holes, respectively, and redistributed them under the action of the built-in electric field. The photogenerated electrons and holes were enriched on the surface of WSe₂ and MoS₂, which greatly improved the efficiency of hydrogen production by photocatalytic water splitting.