The purpose of this work is to establish a national criterion for detection of irradiated foodstufs by use of ESR. Four kinds of spices (paprika, mustard powder, curry powder and ginger powder) were used as test materials to study the feature changes of ESR spectrum and the ESR intensity in the range of absorbed doses from 0 to 15 kGy within the storage period of 220 days. The results show that the ESR spectroscopy of four kinds of spices is obviously different before and after irradiation and the intensity of ESR signal increases with the absorbed dose. The ESR intensity of all the four samples decreases during the storage time, but the ESR method can also be used to identify whether the three kinds of samples are irradiated except mustard powder even after 220 days.