Abstract The selective separation of Mn(II) and Cd(II) as well as regeneration of the complexing agent were conducted by shear induced dissociation coupling with ultrafiltration (SID-UF), and the copolymer of maleic acid and acrylic acid (PMA) was used as complexing agent. At the optimal complexation conditions, pH 6 and P/M (mass ratio of polymer to metal ions) 9, both the rejections of Mn(II) and Cd(II) arrived at more than 99%. The shear stabilities of two PMA-metal complexes at different pHs were particularly investigated using rotating disk membrane and the results indicated that critical shear rates γ c of PMA-Mn complex were lower than that of PMA-Cd at the same pH. According to the difference of the shear stabilities between PMA-Mn and PMA-Cd complexes, the selective separation of Mn(II) and Cd(II) were achieved by SID-UF at 1450 rpm and 1600 rpm, and PMA was regenerated.