Amidoximated mesoporous silica was prepared by grafting and co-condensation methods in this work, respectively. The materials were characterized by FTIR, SEM, XPS and physisorption apparatus. The effects of pH, adsorption time, initial uranium concentration, adsorbent amount and coexisting ions on uranium adsorption by amidoximated mesoporous silica were investigated. The experiment results showed that the uranium adsorption ratio and capacity were improved after modification by amidoxime group. It can be deduced that uranium adsorption could be attributed to the coordination of N atoms in oximido- and amido- in amidoximated mesoporous silica. The uranium adsorption from saline lake brine on amidoximated mesoporous silica were studied. The results showed that the uranium adsorption capacity could reach to 3.5 mg/g with amidoximated mesoporous silica, which was prepared by co-condensation method. Amidoximated mesoporous silica can be a potential adsorbent for uranium extraction from saline lake brine.