Abstract: In this paper, a synergistic system of 2-ethylhexylphosphonic acid mono(2-ethylhexyl) ester (P507) and a bis(2, 4, 4'-trimethylpentyl) phosphonic acid (C272) was introduced into magnetic solid adsorbents and used for adsorbing low-concentration rare earth ions. The adsorption test results of the adsorbent show that when the pH value of solution is 2, the adsorbent has the best synergistic effect, of which the synergy coefficient is as high as 22, and the maximum adsorption capacity is 0.07 mmol/g. However, the increase in ionic strength will produce competitive adsorption, and thus the adsorption capacity of rare earth elements is reduced. The adsorption thermodynamics analysis shows that adsorption is a spontaneous endothermic process, in which adsorption capacity increases with increasing temperature. The results of the kinetic test show that the adsorption process has the highest fit degree with the second-order kinetic model, basically reaching equilibrium after 90 min.