Abstract: In this paper, the adsorption and resolution mechanism of heavy metals Pb²⁺ and Cd²⁺ by modified lignite were studied. Methods: Four single-factor gradient variables (pH value, amount of lignite, adsorption time, adsorption temperature) were designed to carry out the adsorption contrast test before and after the sulfonation. The desorption effects of modified lignite on Pb²⁺ and Cd²⁺ in soil were measured at different pH value gradients. The results showed that the specific surface area of lignite increased from 165 m²/g to 784 m²/g, and the adsorption rate of Pb²⁺ and Cd²⁺ on modified lignite was positively correlated with pH value of solution, addition of lignite, adsorption time and adsorption temperature The adsorption equilibrium was reached at 120 min when the dosage of modified lignite was 6%, and the desorption of Pb²⁺ and Cd²⁺ was the lowest when pH value was 11, and the adsorption has high stability. Conclusions: the adsorption efficiency of modified lignite on heavy metals Pb²⁺ and Cd²⁺ in soil is higher than that before modification, and it can be used as an additive material for the treatment of heavy metal pollution in soil.