As a highly toxic element of coal, arsenic (As) is mainly converted into As₂O₃ vapor during coal combustion. Mineral oxides are effective and abundant sorbents to control As₂O₃ emissions. In this paper, the characteristics of As₂O₃ adsorption by mineral oxides were studied in a two-stage reactor, and the density of states, adsorption sites, and adsorption energies for the adsorption reaction were investigated using molecular simulation. The results demonstrate that CaO is an excellent As₂O₃ sorbent. The As₂O₃ adsorption effect of CaO, MgO, and Al₂O₃ was found to become better with increasing temperature within the range of 300-900 ℃. The order of As₂O₃ adsorption at 300-700 ℃ follows CaO > Fe₂O₃ > Na₂O > MgO > Al₂O₃ > SiO₂, and SiO₂ hardly adsorbs any As₂O₃. At 900 ℃, the melting of Na₂O and Fe₂O₃ greatly reduces their As₂O₃ adsorption capacity. The O atoms in Na₂O/CaO/MgO/Al₂O₃/SiO₂ and the Fe atoms in Fe₂O₃ are the adsorption active sites for As₂O₃. The order of the calculated adsorption energy follows Fe₂O₃ > Na₂O > CaO > Al₂O₃ > MgO > SiO₂, and the As₂O₃ adsorption involves chemical adsorption. The adsorption products are Ca₃(AsO₄)₂, FeAsO₄, AlAsO₄, etc., for which As exists in the form of As³⁺ and As⁵⁺, with As³⁺ transformed into As⁵⁺ with increasing adsorption temperature.