The effect of Ar⁺ injection at six different dosages on peroxidase（POD）activity and isoenzyme expression of japonica rice was analyzed by using polyacrylamide gel electrophoresis.The results showed that the sensitivity of three rice varieties to ion implantation were different as the dosage increased.The POD activity of the injected rice was higher than that of the control and the value at 3000 dose was the highest.It at first increased and then decreased as the dosage increased at the tested range.The diversity of enzymogram band of ‘Nongda 7’ was broader than that of ‘Nongda 13’ and ‘Qiutianxiaoding’,but the band color at 3000 dose showed darker than that at other dosages.