A green solvent extraction process with nonfluorinated quaternary phosphonium ionic liquids for removing uranium from carbonate solutions has been developed. The main advantage of this extraction process is that no molecular diluent and ligand need be added to the organic phase, so the use of volatile organic compounds can be avoided. Uranium was extracted into the ionic liquid (IL) phase as the [Na3UO2(CO3)(3)](-), [Na3UO2(CO3)(2)Cl-2](-), and [NaUO2CO3Cl2](-) anion complexes, and the composition of the IL, Cl- ions, went into aqueous phase, which was determined by electrospin ionization mass spectroscopy (ESI-MS) and Cl- ion test experiment. The extraction mechanism is anion exchange. The maximum loading capacity of the IL is 11.23 g/L. F- ions have no effect on the extraction efficiency for uranium extraction. The stripping of uranium from the IL phase after extraction is difficult using dilute nitric acid and other stripping reagents. The 1 mol/L NaOH solution was used to deposit uranium and this operation was repeated three times to remove uranium from the IL thoroughly.