Abstract: For selective separation of ⁹⁰Sr from HLLW, dodecyl benzenesulfonic acid (DBS) was applied to modified the 4′,4′(5″)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) and a novel silica-based crown ether was synthesized. The successful synthesis of adsorbent was estimated by characterization methods such as SEM, TG-DTA and FT-IR. The leakage of DtBuCH18C6 from the adsorbent is less than 2.03% in 7 mol/L HNO₃, suggesting a good chemical stability of adsorbent. DBS worked as a counter ion to enhance the complex formation between DtBuCH18C6 and Sr(Ⅱ), enhancing the Kd value at 0.5 mol/L HNO₃ to 10 times (355.02 cm³/g), and a synergistic effect with nitrate ions was found at higher HNO₃ concentration. The selective adsorption of Sr(Ⅱ) is proved great, which follows the pseudo-second-order kinetic model and Langmuir model, and the maximum adsorption capacity reaches 42.13 mg/g. Using 1 mol/L HNO₃ solution as eluent, 79% of the adsorbed Sr(Ⅱ) can be eluted from the adsorbent (ratio of eluent vs adsorbent is 0.9 L/g, contact time is 5 h), resulting in effective Sr(Ⅱ) recycle and reuse of adsorbent.