Display omitted •The results of extraction experiment indicated the rank of extraction lithium was: N523 > TBP > DIBK > EA > MIBK > BA.•The stoichiometry of the formed extracted complexes was determined and the mechanisms were revealed.•DIBK can be treated as synergist adding to TBP or N523 extraction system to avoid a third phase. Lithium, as one of the most important green energy, its exploitation and application attract great attention. Solvent extraction has been the most popular method among the techniques of extracting lithium in recent years. In this paper, many kinds of organic extractants, including EA, BA, MIBK, DIBK, N523 and TBP, were selected as organic extractants to investigate the influence on the lithium extraction from high mass ratio of Mg/Li aqueous solution. The results of extraction experiment indicated N523 and TBP were superior to the others on lithium extraction efficiency. Through the investigation of extraction equilibrium, the stoichiometry of the formed extracted complexes was determined. The Raman spectrum showed the FeCl4− formed in the extraction process. The FT-IR results presented the extraction reaction made the functional group of organic extractant shifting to lower wavenumbers, suggesting the new chemical bond form. Further, their solubility was investigated considering the application of organic extractants.