Abstract:The SOD isoenzymes of different soybeans were studied in this experiment and the results showed that: 1. there were 7 SOD isoenzyme bands in all soybean genotypes used in this experiment, 2. the SOD activity (unit/g fr. wt.) in different soybean seeds decreased as the evolutionary process advanced, 3 the SOD activity decreased as the wt./100 seeds increased, and the color of seed coat changed from black to yellow. The relationship between SOD activity and the evolutionary process was discussed.