As a new generation of ultra-wide bandgap semiconductor, β-Ga₂O₃ has significant application value in high-power devices and solar-blind detection devices, attracting extensive attention from researchers in recent years. However, the low symmetry of the monoclinic lattice of β-Ga₂O₃ leads to anisotropic formation energies for the planar defects, with the (100) twin boundary exhibiting a lower formation energy and being prevalent in β-Ga₂O₃. To explore the control methods and mechanisms for the formation of the β-Ga₂O₃ (100) twin boundary, the interactions between the Al/In dopants and the (100) twins using first-principles calculations were investigated in this paper. Analysis of the structure, energy, and electronic properties of the Al/In-doped β-Ga₂O₃ (100) twin boundary system indicates that the substitution of Ga in the twin system by Al/In significantly affects the formation energy of the (100) twin boundary. Notably, the incorporation of Al consistently raises the formation energy of the (100) twin boundary without significantly altering the bandgap, shifting the band edges, or introducing additional impurity levels within the bandgap. Therefore, Al/In incorporation is predicted to be a potential strategy for influencing the formation of β-Ga₂O₃ (100) twin boundary. An appropriate incorporation of Al/In may help suppress the formation of the (100) twin boundary and improve the quality of β-Ga₂O₃ crystals.