Phosphoric acid-functionalized mesoporous silica material was prepared by copolycondensation using P123 as the soft template and diethylphosphatoethyltriethoxysilane as the functional monomer. It was used for highly efficient selective adsorption and separation of La(III). By adjusting the ratio of the silicon source to functional monomer, the difference of the adsorption material structure and the change of adsorption performance were explored. When the ratio of the silicon source to functional monomer is 9/1, the phosphoric acid-functionalized SBA-1.5 (named S2) exhibits a highly ordered hexagonal cell structure. Saturated adsorption capacity of La(III) on S2 is 114.81 mg g(-1) at 25 degrees C and 7.0 pH, which is much larger than other reported adsorbents. In addition, the adsorbent S2 has excellent adsorption kinetics: the adsorption equilibrium can be quickly concluded within 60 min. The distribution coefficient (K-d) of S2 to La(III) is 725 mL g(-1), and that of Nd(III) and other ions is about 200 mL g(-1). This indicates that the phosphoric acid-functionalized adsorbent has strong selectivity in the process of adsorption and separation of La(III). Cyclic performance tests indicate that the adsorbent has excellent regenerability. The above results indicate that the phosphoric acid-functionalized SBA-15 adsorbent (S2) has a promising application in the actual adsorption separation of La(III).