Abstract: The allelopathy of the exotic invasive plant Solidago canadenis L. was studied, which study would help understand the inhabition to other plants and be of paramount significance to agriculture. The extract from the organs above ground of Solidago canadenis was used to treat the seeds of three plant seeds, this study determined the seeds germination rate and the final germination. The results were as follows：(1)the allelopathic effects of Solidago canadenis does exist; (2)Higher concentration of the water extract of the host plant could restrain the traits of germination of three plant, including the final percent germination, germination rate and the trend of germination. In three experimented species, the effect of water extract from host plant on Poa annua and Brassia campestris were more significant than Basella rubra. This research using the experiment of seed germination preliminarily proved the chemical mechanism of the host plant.