The interfacial electronic structure of Fe₃O₄/BaTiO₃ heterostructures was investigated using first-principles calculations. Owing to the two TiO-polarization directions, Fe_BO-terminated models show different interfacial binding strengths. Compared with the OTi–Fe_BO model, the TiO–Fe_BO model shows a spin polarization of 100% due to the hybridization effect of Ti 3d and Fe_B 3d at the Fermi level, which can be modulated by the electric field and TiO polarization directions. Negative electric field can control the strength of the hybridization of the interfacial Ti and O with Fe_B, but the positive electric field has no significant effect on it. The tunable high spin polarization at Fe₃O₄/BaTiO₃ interfaces has potential applications in spintronic devices.