Abstract: This articel dealt with the studies on chromosome aberration induced with 60Co gamma ray in a species of gamasid. Eulaelaps shanghaiensis (Acari, Gamasina). Ghromosome aberration of the gamasid mite egg cells following differnet doses of 60Co gamma ray(1-50 Krad) had been studied. Chromosome gap(csg), fragments(f), minute (min), ring chromosome (r), pulverization (prz) and polyploid were found. Chromosome fragments are most frequent chromosome aberration. micronuclei were also formed. The rates of chromosome aberrations were increased with the radiation dose. By means of an analysis of statistics, a curvilinear regression relationship between irradiation dose and chromosome aberration rate, Y=3.27+14.49lg(X+1), was revealed.