Hypoxic　tumor　microenvironment　(TME)　is　closely　linked　to　tumor　progression,　heterogeneity　and　immune　suppression.　Therefore,　the　development　of　effective　methods　to　overcome　hypoxia　and　substantially　enhance　the　immunotherapy　efficacy　remains　a　desirable　goal.　Herein,　we　engineered　a　biocompatible　Au　core/Pt　shell　nanoparticles　(Au@PtNPs)　to　reoxygenate　the　TME　by　reacting　with　endogenous　H2O2.　Treatment　with　Au@PtNPs　appeared　to　improve　oxygen　in　intracellular　environments　and　decrease　hypoxia-inducible　factor-1　alpha　expression.　Furthermore,　the　integration　of　high　catalytic　efficiency　of　Au@PtNPs　with　cytokine-induced　killer　(CIK)　cell　immunotherapy,　could　lead　to　significantly　improve　the　effect　of　CIK　cell-mediated　cytotoxicity.　These　results　suggest　great　potential　of　Au@PtNPs　for　regulation　of　the　hypoxic　TME　and　enhance　immune　cell　mediated　anti-tumor　immunity.