Abstract: The modified attapulgite was obtained by acid activation and loaded magnetic nano-ferrite composite modification. The applicability of attapulgite in the adsorption furnace of semi-volatile heavy metal PbCl₂ vapor in different flue gas atmosphere was explored. Besides, the adsorption mechanism of PbCl₂ vapor was investigated by combining FT-IR, BET, XRD and DFT theoretical calculation. The results show that acid activation increases the proportion of surface-active sites by decomposing impurities in the original ore, and the double active adsorption sites formed by the composite modified iron-based oxides and attapulgite lattice oxygen significantly enhance the adsorption capacity of PbCl₂. The maximum adsorption capacity of Fe/HP₂ samples with the mass ratio of 1∶2 is 67.62 (mg PbCl₂/g adsorbent). When the high-temperature flue gas contains O₂, SO₂ and a small amount of H₂O, it can enhance the adsorption capacity of modified attapulgite. In addition, DFT theoretical calculations show that H₂O, O₂, SO₂ and PbCl₂ all undergo chemisorption on the surface of ATT(110), and it also demonstrates that H₂O promotes the adsorption of PbCl₂ on the surface of ATT(110) and Fe/ATT(110) through co-adsorption. Weaker adsorption of PbCl₂ at the adsorbed oxygen sites formed by H₂O molecules instead of at the lattice oxygen sites can be preferentially bond to double active sites (the lattice oxygen sites and the oxygen site) in the iron oxide clusters through strong interactions on the Fe/ATT(110) surface.