It is well know that EDTA is the sensitizing agent which has been reported by many papers concerned. EDTA was used in plant together with other aberrant factors in order to increase the frequency of chromosome aberration. In this test, the cells of sunflower root tip were treated by EDTA with the same concentration but different duration, i.e. 3, 5 and 7 hours. The results indicated that the three treatments of EDTA induced high frequency of chromosome aberration. Moreover, the frequency of chromosome aberration increased with the increasing of treatment duration.