Abstract: The genetic disorder ataxia-telangiectasia (AT) is characterized by immunodeficiency, progressive cerebellar ataxia, gonadal abnormalities, radiosensitivity, and cancer predisposition. In this paper, the signal transduction of AT are reviewed, including ATM (AT mutated) gene and clinicalsymptoms, some transoription factors in the signaling pathway induced by ionizing radiation, cell cycle checkpoint defects, durative oxidative stress and cell apoptosis.