Abstract: As human space activities extend from low Earth orbit to the cislunar region and interplanetary space, space radiation has emerged as a fundamental safety issue constraining mission reliability and the feasibility of long-term human presence beyond Earth. Characterized by multiple sources, high particle energies, and strong temporal variability, the space radiation environment poses persistent and unpredictable risks to spacecraft systems and human health. For deep-space exploration missions beyond geomagnetic shielding, the spatiotemporal behavior and interaction mechanisms of space radiation become increasingly complex, placing higher demands on the effectiveness of radiation protection. In response, a systematic framework integrating environmental characterization, detection technologies, and protective interventions is needed. This paper reviews the characteristics of the space radiation environment, methods for radiation detection, as well as passive, active, and biomedical radiation protection approaches. Research progress of representative space missions is summarized and discussed. These studies provide a theoretical basis for radiation safety management in manned spaceflight and offer important references for the development of protection strategies and engineering paradigms in deep space exploration.