The applications of room-temperature ionic liquids (RTILs) in separation of high level radioactive nuclides demand a comprehensive knowledge of the stability and metal ion extraction of RTILs under radiation. Herein, we assessed the influence of gamma-irradiation on the [C(4)mim][NTf2]-based extraction system, where [C(4)mim](+) is 1-butyl-3-methylimidazolium and [NTf2](-) is bis(trifluoromethylsulfonyl)imide, by solvent extraction of Sr2+ using irradiated [C(4)mim][NTf2] in combination with dicyclohexyl-18-crown-6 (DCH18C6). It was found that the degree of extraction for Sr2+ from water to irradiated [C(4)mim][NTf2] decreased compared with that to unirradiated [C(4)mim][NTf2], and the decrement enhanced obviously with increasing dose. NMR spectroscopic probe analysis revealed the formation of acids during irradiation of [C(4)mim][NTf2]. The decrease of Sr2+ partitioning in irradiated [C(4)mim][NTf2] is attributed to the competition between H+ with Sr2+ to interact with DCH18C6. Accordingly, washing irradiated [C(4)mim][NTf2] with water gives a simple way of ionic liquid recycling. Furthermore, the degree of extraction for Sr2+ from 3 mol.L-1 nitric acid solution to [C(4)mim][NTf2] is independent of the irradiation of [C(4)mim][NTf2] since the amount of the radiation-generated H+ is negligible in such a high acidic solution.