A novel zwitterionic polymer ionic liquid functionalized magnetic nanospheres, shortly as Fe3O4@PCL-PILs, is synthesized by grafting ionic liquid VimCOOHBr onto polymer ε-caprolactone (PCL) modified magnetic nanospheres via esterification and surface-initiated free radical polymerization. This established synthesis strategy offers the obtained magnetic nanospheres with well-defined core-corona structure, compact grafting layer, favorable zwitterionic and negative-charged surface, and high magnetic susceptibility. The as-prepared Fe3O4@PCL-PILs nanospheres exhibit typical "zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC)" behaviors toward protein binding, and selectively adsorption of glycoprotein is achieved. The adsorption capacity of the magnetic nanospheres toward Immunoglobulin G is high up to 1136.4 mg g-1, and the captured Immunoglobulin G could be efficiently recovered by using 0.5% NH3 H2O (v/v) as stripping reagent, providing a recovery of 80.5%. Fe3O4@PCL-PILs nanospheres are then employed as sorbent for the selective isolation of Immunoglobulin G from human whole blood, obtaining high-purity Immunoglobulin G as demonstrated by polyacrylamide gel electrophoresis assays.