Abstract: The chitosan with low molecular weight was prepared by γray degradation method. The influence of irradiation dose on the radiation degradation of chitosan was studied in heterogeneously aqueous solutions of H₂O₂, NaBH₄ and L-α-alanine. The degradation products were characterized by FTIR and UV-VIS. The degradation of chitosan is the most quickly in theH₂O₂, because of the concentrations of OH radicals increased. The white degree of irradiation degraded chitosan is the highest in NaBH₄ or L-α-alanine solution. UV and FTIR analyses manifest that no obvious differences in the main chain structure and deacetylation degree between irradiated and un-irradiated chitosans, but the carbonyl group forms in the molecules of the irradiated chitosan. The results show that γ-ray can be expected as an effective way to control the molecular weight of chitosan.