Abstract: We adopted lattice Boltzmann method to simulate double diffusion mixed convection, fluid-solid conjugate heat transfer and adsorption process in a lid-driven composite enclosure filled with homogeneous medium at pore scale. Influences of buoyancy ratio Br (-100 ≤ Br ≤ 100) and adsorption rate constant k₁ (0.001 ≤ k₁ ≤ 0.005) on characteristics of heat and mass transfer were compared at porosity ε=0.79, Prandtl number Pr=0.7, Grashof number Gr=10⁴ and Lewis number Le=1.0. Streamlines, isotherms, isoconcentrations, adsorption capacity (C_S), average Nusselt number Nu_av and Sherwood number Sh_av of the left heated wall under different parameters were discussed in detail. It shows that Br affects adsorption by changing concentration distribution around medium in flow field; Increasing k₁ improves significantly adsorption efficiency and adsorption capacity.