Abstract: The influence of the crystal structure of cassiterite surface and the activation of lead ion on the adsorption process of benzohydroxamic acid and salicylic oxime on cassiterite surface was studied by density functional theory. The electronic structure of cassiterite (100) after lead adsorption is analyzed by using the density of States and frontier orbital theory. The results show that the adsorption of lead ions on cassiterite (100) will reduce the reactivity of the surface oxygen atoms and increase the reaction sites on the surface. According to the frontier orbital theory, the interaction energy of Benzohydroxamic acid and salicylic hydroxamic acid and cassiterite (100) surface is compared from the energy point of view, and the essence of hydroxamic acid can be used in the flotation of cassiterite.