A mutant with stay green features was created by 60Co γ–ray radiation of the soybean Kefeng 14 seeds and 20 mutant lines were obtained from this mutant in years of selective breeding. The stay green features of these mutant lines were identified by comparing the growth period, biological characteristics, chlorophyll content of leaves in the late growth stage and the anti-aging test of leave. The results showed that the mutant lines had longer duration of the stay green features in the leaves and seed pods, and the seeds had green seed coat and green cotyledon. The flowering times were different for the 20 mutant lines, however, the mature periods all were later than Kefeng14, The chlorophyll content in the leaves of the mature were decreased slowly during seed filling stage even contained more chlorophyll before leaf dry in the mature period , while the chlorophyll content in Kefeng 14 were declined rapidly. The leaf-induced senescence test also showed that these mutant lines had stronger anti-aging than the original Kefeng 14.