This article presents the preparation of a new type of metal ion selective resin based on phosphoric acid functionality and its application on the separation of Mo and V ions. The metal ion selective resin can be prepared by immobilizing D(2)EHPA onto the surface of porous Amberlite XAD-4 resin, employing a solvent-nonsolvent process. The amount of immobilized D(2)EHPA is as high as 2.5 (mmole D(2)EHPA/g of resin). Solvent extraction experiments indicated that D(2)EHPA can extract more Mo ion than V ion. The separation of Mo and V ions is best accomplished at pH 6. Adsorption isotherm experimental results show that D(2)EHPA-modified Amberlite XAD-4 resin can also adsorb more Mo ion than V ion. Within the range of experiment, the amount of adsorbed Mo ion can be as high as 0.04 (mole Mo/mole D(2)EHPA), while the amount of adsorbed V ion is less than 0.01 (mole V/mole D(2)EHPA). However, due to the formation of polyion in high concentration solution, the Mo ion distribution ratio between modified resin and liquid phase decreases with increasing Mo ion concentration. The initial concentration of Mo ion should be lower than 0.01 M to have effective separation results. The selective extraction results using series contacts of solution mixtures with resins further demonstrated the feasibility of D(2)EHPA-immobilized Amberlite XAD-4 resin for the separation of Mo/V mixed ion solution. After only seven batches of contacts; the relative ion concentration of V ion increased from 67% to more than 96%, while the relative ion concentration of Mo ion decreased from 33% to less than 4%.