Abstract: The effect of γ-ray of cobalt-60 (50r-100000r) and 14 Mev fast neutron (1.4×10~(12) neutrons/cm²) on cyanocobalamin and its aqueous solutions has been studied. The result indicate that minimum destructive dose of γ-ray of cobalt-60 to diluted cyanoco-balamin solution was between 2000r and 3000r. When the irradiation dose reached 100000r, more than 60% of the cyanocobalamin deteriorated.The destruction features of γ-ray of cobalt-60 are: dilute solution is more easily destructible than concentrated ones, and cyanocobalamin is not easily in the solid state. The destructive degree increased with the increase of irradiation dose. The characteristic absorption peaks at 278nm, 361nm and 550nm gradually became more flat and lower as the irradiation dose increased. The cyanocobalamin content decreased with the increase of irradiation dose and yielded several degradation products.The fast neutron, under the experimental conditions, showed no obvious destructive effect on aqueous cyanocobalarnin solutions.