A　novel　sulfonate-bonded　covalent　organic　polymer　(COPTPBA-BPDA@SA)　with　mixed-mode　interactions　of　hydrophobic　and　cation-exchange　was　synthesized　and　exploited　as　sorbent　for　on-line　solid-phase　extraction　(on-line　SPE)　of　ß2-receptor　agonists.　The　successful　synthesis　of　COPTPBA-BPDA@SA　was　confirmed　by　the　characterization　of　SEM,　XPS　and　FT-IR.　Due　to　the　excellent　mixed-mode　extraction　ability　towards　the　positively　charged　ß2-receptor　agonists　and　the　good　anti-interference　performance,　COPTPBA-BPDA@SA　was　introduced　into　on-line　SPE-HPLC　system　for　selective　extraction　of　ß2-receptor　agonists　in　pork　and　pork　liver.　Via　the　optimization　of　the　extraction　condition,　including　formic　acid　percentage　and　ACN　percentage　in　the　sampling　solution,　the　mixed-mode　extraction　mechanism　of　COPTPBA-BPDA@SA　was　investigated.　The　elution　condition,　such　as　the　pH　value,　formic　acid　percentage　and　ACN　percentage　of　the　eluent　was　also　optimized　for　the　desired　SPE　performance.　Under　the　optimized　condition,　COPTPBA-BPDA@SA　revealed　better　purification　performance　than　COPTPBA-BPDA　without　sulfonating.　The　LODs　for　ß2-receptor　agonists　were　in　the　range　of　0.08–0.22　μg/kg,　and　the　recoveries　in　different　samples　at　three　spiked　levels　(0.4,　4.0,　8.0　μg/kg)　were　ranged　from　83.2%　to　98.5%　with　RSDs　less　than　5.2%,　which　indicated　the　satisfactory　mixed-mode　extraction　ability　of　COPTPBA-BPDA@SA　as　well　as　the　good　applicability　of　the　developed　method.　©　2020　Elsevier　B.V.