The strontium ions extracted from the aqueous phase into 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide(C_2mimNTf2) with dicyclohexyl-18-crown-6(DCH18C6) was stripped effectively by supercritical CO_2(sc-CO_2).Hexafluoroacetylacetone(HFAA)-acetonitrile was found to be an excellent modifier of sc-CO_2 to enhance the stripping efficiency.In the orthogonal array design(OAD),OA_(25)(5~5)matrix was employed to optimize the stripping of Sr(Ⅱ) from the DCH 18C6-C_2mimNTf_2 system.Effects of five experimental factors:temperature,pressure,concentration of HFAA,static and dynamic extraction times as well as each factor at five-levels on the stripping of Sr(Ⅱ) were optimized.The effects of these parameters were treated by the analysis of variance(ANOVA).The results showed that Sr(II) could be nearly 100%extracted from the IL phase at 308 K,30 MPa,40 min of dynamic extraction and 60 mmol·L~(-1) HFAA in acetonitrile,respectively.Finally,the stripping mechanism was studied by ESI-MS. The strontium ions extracted from the aqueous phase into 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (C_2mimNTf2) with dicyclohexyl-18-crown-6 (DCH18C6) was stripped effectively by supercritical CO_2 (sc-CO_2) .Hexafluoroacetylacetone (HFAA ) -acetonitrile was found to be an excellent modifier of sc-CO_2 to enhance the stripping efficiency. In the orthogonal array design (OAD), OA_ (25) (5~5) matrix was employed to optimize the stripping of Sr (Ⅱ) from the DCH 18C6-C_2mimNTf_2 system. Effects of five experimental factors: temperature, pressure, concentration of HFAA, static and dynamic extraction times as well as each factor at five-levels on the stripping of Sr (Ⅱ) were optimized.The effects of these parameters were treated by the analysis of variance (ANOVA). The results showed that Sr (II) could be nearly 100% extracted from the IL phase at 308 K, 30 MPa, 40 min of dynamic extraction and 60 mmol·L ~ -1) HFAA in acetonitrile, respectively. Finally, the stripping mechanism was studied by ESI -MS.