Abstract: In modern egg processing plant, eggshell crack detection in egg sorting and packaging is a major bottleneck for automation because it is largely done by human workers. In order to find out quick eggshell crack detection nondestructively for on-line application, frequency responses of an egg excited with a light mechanical impact at different locations on the eggshell were studied. Through analyzing the response frequency by the computer, it was found that the characteristic response frequency of intact eggs changed in a small range but the characteristic response frequencies of cracked eggs were heterogeneous and varied in a larger frequency range. By analyzing coefficient of variation (CV) of the four characteristic response frequencies at the chicken egg equator zone, a sorting algorithm to detect crack eggs was developed. Based on this method, the detecting rate was 91% for cracked chicken eggs and 87% for the total chicken eggs.