The electronic structure of monolayer WSe₂/BiIrO₃(111) interfaces is investigated by first-principles calculations. The different polar directions of bilayer BiIrO₃(111) can induce the p- or n-type doping of WSe₂, indicating that the conductivity of monolayer WSe₂ can be effectively modulated by switching the polarization of bilayer BiIrO₃(111). Meanwhile, in B1 and B4 models, the spin splitting energies of WSe₂ are 413.7 and 416.6 meV, which decrease by 52.9 and 50.0 meV compared to that of pristine monolayer WSe₂ of 466.6 meV. Additionally, by applying a perpendicular electric field of 0.1 V nm⁻¹, the spin splitting can be increased from 413.7 to 421.5 meV. However, spin splitting shows robustness against large electric fields. The results are useful in the design of novel two-dimensional transition metal dichalcogenide devices.