Until recently, high organic phase volume and the addition of a large amount of surfactants have been two major disadvantages of conventional high internal phase emulsions (HIPEs) templates in the construction of porous adsorbents. Herein, a facile and novel tunable superporous magnetic adsorbent (MSPA) was synthesized by the polymerization of the green surfactant-free (soybean oil)-in-water Pickering medium internal phase emulsion (O/W Pickering MIPEs), which was stabilized synergically by the magnetic yeast (MY) and chitosan (CTS). It is interesting that the extremely stable surfactant-free Pickering-MIPEs can be obtained through the fine synergistic effect between MY and CTS at the oil-water interface, and the pore structure of the magnetic adsorbent can be easily adjusted by changing the ratio of MY to CTS, as well as the external pH. The obtained MSPA with abundant -COO⁻ and -NH₂ functional groups had a fast capture rate and high adsorption capacities for radioactive Rb⁺ and Sr²⁺ ions, respectively. The saturation adsorption capacities of 168.98 and 151.91 mg/g for Rb⁺ and Sr²⁺ can be achieved within 25 or 10 min, respectively. Moreover, the MSPA had excellent regeneration ability and reusability. This work provided a feasible and environmentally friendly pathway for preparation of the superporous magnetic adsorbent with tunable porous structure for adsorption and separation application.