An optimum reagent was selected to decontaminate the radioactive soil near nuclear facilities by using the developed vertical electrokinetic-flushing equipment, and the optimum remediation conditions were established to obtain a higher remediation efficiency and a minimum waste-solution volume. Namely, the acetic acid was selected as an optimum reagent due to its higher remediation efficiency. The average removal efficiency by a vertical electrokinetic-flushing remediation was 4.6% more than that by a vertical electrokinetic remediation. The optimum remediation conditions were suggested to be when the acetic concentration is 0.01M, the injection rate of the reagent is 2.4ml/g and the remediation period is 20 days for the vertical electrokinetic-flushing equipment of a 8.3L volume. In these conditions, the removal efficiencies of Co2+ and Cs+ were 98.3% and 88.8%.