CD47 is a well-defined immune checkpoint receptor protecting cells from the phagocytotic elimination by immune cells including macrophages via engagement of SIRPα on cell surface32,33. Therapeutic benefits by targeting CD47 are demonstrated in a series of pre-clinical and clinical studies in an array of human cancers34,35,36,37 including GBM treated with radiation and anti-CD47 antibody38, and CD47 is overexpressed in radioresistant breast cancer cells37. Using radioresistant GBM cells, regrown syngeneic mouse GBM, and recurrent tumors of GBM patients, this study reveals an immune evasion function of radioresistant GBM cells through FAO metabolism boosted CD47 anti-phagocytosis. CD47 transcription is activated via FAO-derived acetyl-CoA that acetylates RelA K310 to upregulate CD47 transcription. Blocking FAO not only inhibits aggressive growth of radioresistant GBM cells but diminishes the orthotopically regrown mouse tumors by RT combined with anti-CD47 antibody. Blocking the acetyl-CoA-CD47 pathway is a potential therapeutic approach to sensitize radioresistant tumors to CD47 immunotherapy.