The distribution of Cynanchum komarovii and Astragalu svariabilis in Alxa Left Banner was investigated in June, 2013 and 2014 with quadrat sampling method. There were 10 sample plots in the investigation area,and 200 small quadrats were set totally.In a two-year survey,the results showed that the distribution areas of C. komarovii and A.variabilis were 3.95*10~4 hm~2,4.63*10~4 hm~2 and 0.13*10~4 hm~2,1.02*10~4 hm~2 respectively, which showed a marked decrease with previous results. This might occur because climate change during the years, and implementation of the "Returning Grazing-Growing" policy in local area, and the occurrence of pests on a small scale as well. Through a further analysis, It was showed that the relative abundance of the two poisonous plants hardly influenced the species diversity in the community.