Considering the possible existence of three types of compounds, namely K₃Sb, K₂CsSb and Cs₃Sb in the growth of K₂CsSb photocathode, a first-principles study based on density functional theory was employed to establish the cubic bulk models and the (111) surface models for the three types of antimonide cathode materials. Through theoretical calculations, electronic structures and optical properties were obtained, wherein band structures, densities of states and optical properties were acquired for bulk models, and work function, optical properties and surface energy were calculated for (111) surface models. The results demonstrate that, as for the three types of antimonide cathodes, in the radiation energy range of 2.4~3.2 eV produced by interaction between neutrinos and scintillators, the absorption and relectivity of K₂CsSb bulk material are close to those of Cs₃Sb and K₃Sb ones, whereas the values of K₂CsSb (111) surface material are lower than those of Cs₃Sb and K₃Sb ones. In addition, K₃Sb has the narrowest bandgap, maximum work function and maximum surface energy, while Cs₃Sb has the minimum surface energy and its work function is close to that of K₂CsSb, but its band gap is smaller than that of K₂CsSb. By contrast, K₂CsSb with the widest bandgap has the smaller work function and surface energy. Therefore, K₂CsSb photocathode is suitable to serve as a stable and high-efficient photoemitter in the blue-violet spectral region.