The inner synergistic effect of bifunctional ionic liquid extractant (Bif-ILE) for solvent extraction is reported for the first time using [tricaprylmethylammonium][di-2-ethylhexylphosphinate] ([A336][P204]) as n extractant for Eu(III), which can be attributed to better stability and hydrophobicity of the complex formed by [A336][P204] with Eu(III). Some other Bif-ILEs are also found to have the similar inner synergistic effect. Distribution coefficient, stripping property and extraction mechanism of the novel extraction protocol are discussed in this report. The study contributes towards acquiring a new understanding of synergistic extraction and task specific ionic liquid (TSIL), furthermore, providing a positive influence on their potential application in analytical chemistry.