The double hydrophilic ionic liquid block copolymer (ILBC), poly(ethylene glycol)-block-poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)] (PEG₁₁₃-b-PMMPImB₂₄), was synthesized through RAFT polymerization of 1-methyl-3-(2-methacryloyloxy propylimidazolium bromine) using PEG-CTA as a chain transfer agent. Directly interacting with AuCl₄⁻ in aqueous solutions, the micellization of self-assembling PEG₁₁₃-b-PMMPImB₂₄ was induced via the anion responsive properties of the ILBC. Then, the composites of polymeric micelle encapsulated gold nanoparticles (GNPs) were successively obtained by the reduction of AuCl₄⁻in situ. At a lower molar ratio of AuCl₄⁻ to imidazolium, the obvious vesicle structures of the polymeric micelles with AuCl₄⁻ and the composites with GNPs were formed and the distribution of GNPs in the polymersome walls appeared to be uniform in size. The spherical micelles with highly packed GNPs were also obtained by increasing the content of AuCl₄⁻. These results indicate that the unique chemical and physical properties of PILs in the micellar core can control the micellar morphology and the distribution of GNPs in a confined space.