Abstract: The effects of invasion by Solidago canadensis on plant species diversity in semi-natural woodland were studied.Results showed that plant diversity of the woodland decreased with severe invasion by S.canadensis.No significant differences were found between the control plot and the spreading plot(where the coverage of S.canadensis was less than 40%);nevertheless,Simpson index,Shannon-Wiener index,and evenness index of the control plot and spreading plot were higher than the invaded plot(where the coverage of S.canadensis was more than 70%).Plant species diversity varied greatly among the different plots in different seasons.Simpson index and the Shannon-Wiener index decreased linearly from April to November 2009,but increased again in January 2010.From June to October 2009,plant diversity suffered the most damage from the invasion of S.canadensis as its rapid vegetative propa-gation capacity played a key role in successfully competing with indigenous plants for limited resources.This notorious invasive plant caused severe and negative effects on plant diversity in woodlands by conquering habitat through high vegetative propagation,in spite of the limitation of growth under woodlands.