A study was carried out to establish the detection method for irradiated cereals. Starchs were ground and irradiated at 2.5, 5.0, 7.5, 10 and 15 kGy using a Co-60 irradiator. The viscosities decreased in all samples by increasing irradiation dose. The viscosity of the potato, corn and sweet potato from Korea dropped from 35.00$pm$ 0.34, 11.86$pm$0.86 and 14.02$pm$0.62 in the control to 11.38$pm$0.92, 2.98$pm$0.80 and 2.74$pm$0.80, respectively, in the samples irradiated at 15 kGy. These trends were similar to samples from China. Regression expression and coefficients of viscosity of potato, corn and sweet potato starch from Korea were 0.97 (y=-4.6197x+38.284), 0.88 (y=-1.5146x+12.023) and 0.88 (y=-1.5146x+12.023), respectively, those of viscosity of starches from China were 0.69 (y=-28.849x+152.25), 0.81 (y=-3.38x+20.56) and 0.88 (y=-2.668x+18.505) at 50 rpm. All samples resulted in a decrease in specific parameter by increasing rpm after irradiation. Parameter values showed dose-dependent relationship between unirradiated and irradiated samples and indicated that all values of unirradiated samples were higher than the those of irradiated ones. These results suggest that the detection of irradiated potato, corn and sweet potato starch at various irradiation doses is possible by the viscometric method.