Abstract: The quantitative adsorption mechanism of sulfur-chelating based straw cellulose (TMCS) was studied. Frontier orbitals and quantum chemical reactivity index showed that the 6226 molecular structure of TMCs had the strongest nucleophilic ability compared with other possible molecular structures, and was determined to be the most important adsorption structure. Its Fukui function, electrostatic potential, Mulliken charge and adsorption energy were calculated to determine quantitatively the major role of S atom in -C(NH₂)＝S and N atom in -N-/=N—H during the process of Cd(Ⅱ) adsorption. The adsorption theory of chelating cellulose was studied quantitatively from many aspects, and this research would have guiding significance for the design of cellulosic modification.