Abstract: In order to study the change rule of the seeds/stem ratio and major disease (the grey speck and root rot disease) resistance of main soybean cultivars in Sanjiang Plain of different eras, 18 main cultivars of different eras with the same maturity time were selected as test materials and a field investigation was conducted. The results showed that the seeds/stem ratio changing trend had been improved continually along with the years. The range ability was from 0.44 to 0.88 and the range was 0.44. The growth speed was 0.73%. So the seeds/stem ratio was a key factor for the increase of soybean yield. There were great changes on the grey speck disease resistance level among different soybean cultivars. The disease resistance was enhanced, indicating that the harm of the grey speck disease had been effectively controlled. The soybean cultivars of the 1950s and 1960s were all susceptible to grey speck disease and the cultivars of 1970s were transition ones. The soybean cultivars after the 1980s all had moderate resistance or resistance to grey speck disease. The soybean cultivars were all susceptible to root rot disease except individual cultivars‘( Suinong4’,‘Hefeng45, 55’and‘Heinong48’). The root rot disease resistance showed a stage improvement trend. The resistant cultivars accounted for 22.22% and the susceptible cultivars accounted for 77.78%. This result showed that the root rot disease had not been controlled effectively and needed to be solved in breeding and production at present.