Abstract:Amorphological comparison study between the normal chromosome group and dis -torted by 60Co γ irradiation of Chinese citrus fly Dacus citri(Chen)was conducted.The chro-mosome nunlber was 2n=12,the total chromosome length was 56.2μm,the indivlduallengths of chromosomes ranged from 6.52~1.10μm,and the karyotypic formula, 2n=4m+lsm+1t,belonged to medium asymmetric type. After 4.5,9 and 12 krad of irradiation tothe pupae,the chromosomes in reproductive cell were broken and adhered each other;Chro-mosomal defciency.translocation and reversion was caused and the cell division was ob-structed. The gametes were sterilized and even diet out.