Abstract: The process of preparing polyantimonic acid exchanger by oxidative reflux method from antimonous oxide using hydrogen peroxide solution as oxidant was studied. This kind of ion-exchange material has a high selectivity to Sr²⁺ over Y³⁺ among other inorganic ion exchangers that have been reported when the ion-exchange material is used as a separating medium in Sr²⁺-Y³⁺ solution. The condition of the preparation was investigated by orthogonal experimental method. The optimum reaction conditions of gaining higher distribution coefficients for Sr²⁺ and Y³⁺ are as follows: reaction temperature 60 ℃, 40 mL aqueous and 12 mL hydrogen peroxide solution were mixed with 10 g antimonous oxide, reaction time 120 min. Physicochemical properties of polyantimonic acid exchanger were also studied. The results show that the polyantimonic acid is a kind of cation exchanger.