Abstract: Abstract: Objective To observe the AFLP changes of 137Cs-γ irradiation on the laboratory red crucian carp, and to explore the effect of different doses of γ-rays on the laboratory red crucian carp DNA polymorphism. Method According to the preliminary experimental results , laboratory red crucian carp C1HD was randomly divided into 5 groups, 10 tails / group, namely blank control group, 1 / 16 LD50 , 1 / 8 LD50 , 1 / 4 LD50, 1 / 2 LD50, 4 irradiation groups of 1. 94 Gy, 3. 88 Gy, 7. 76 Gy, 15. 53 Gy, and blank control group were set, and the laboratory red crucian carp was irradiated once and for all by using a biological irradiator. The blood DNA of the laboratory red crucian carp before and after irradiation was extracted and amplified by AFLP-PCR. The polymorphism information content (PIC) , gene heterozygosity (H) and Shannon information index (I) was analyzed. Result Before the laboratory red crucian carp was treated with 137Cs-γ irradiation, the gene polymorphism information content (PIC) , Nei’ s gene diversity (H) and Shannon’ s Information index (I) in normal laboratory red crucian carp is 45. 20%, 0. 19 and 0. 28. After 137Cs-γ irradiation treatment, they are 72. 27%, 0. 28 and 0. 41 respectively, which showed the genetics index rise. Conclusion After 137 Cs-γ nuclear radiation treatment, PIC and H in laboratory red crucian carp are higher. AFLP marker in laboratory red crucian carp C1HD can be used to monitor nuclear contamination