Abstract: The present disclosure relates to a biomarker, a kit, and a method for detection or auxiliary detection of proton irradiation and use thereof, and belongs to the field of biotechnology. The present disclosure provides a microbial biomarker for detection or auxiliary detection of proton irradiation, in which the microbiota includes at least one of Cyanobacteria, Epsilonbacteraeota, Anaerovorax and Helicobacter. In the present disclosure, whether a subject to be tested is exposed to proton radiation is accurately determined by detection of an abundance or relative abundance of DNA of the microbial biomarker. This is conductive to timely accident rescue, casualty treatment and clinical treatment application, which is of great significance to radiation treatment.