Disclosed are an amino mercaptan compound and a preparation method therefor and the use thereof in protection against radiation. The compound has the structure of formula I, wherein A1 is selected from -C(O)NR8-, -S(O)2-NR8-, -S(O)NR8- and -R7-NR8-； A2 is selected from carbonyl, sulfonyl, sulfinyl, substituted or unsubstituted C1-6alkyl； R1, R2, R5 and R6 can be the same or different, and are selected from hydrogen, substituted or unsubstituted C1-C5alkyl or heteroalkyl； n is an integer from 0 to 20,000； R3 and R4 are independently selected from hydrogen, X, substituted or unsubstituted C1-6alkyl； X is selected from F, Cl, Br and I； R7 is selected from substituted or unsubstituted C1-C6alkyl； and R8 is selected from hydrogen, substituted or unsubstituted C1-C6alkyl. The compound has the effect of decreasing the biological damage induced by ionizing radiation, and at the same time also has the effect of prolonging the lifetime and survival rate of an animal exposed to radiation, and has significant alleviating effects on the side effects of radiotherapy. In addition, the compound has a comparatively low toxicity. The present invention opens up a new approach for preventing, treating and curing ionizing radiation damage.
