Abstract: In order to explore the pathway of Eupatorium catarium invading Hainan Island, we studied the relationship of the species from Hainan Island and west Guangdong province. We selected 8 populations of E. catarium in Hainan Island and Guangdong for the study on the genetic diversity, morphology and the characteristics of biomass distribution among them. Based on the dendrogram analysis of genetic distance, we found that the 5 populations from Hainan Island were in the first cluster, and the 2 populations from Yangjiang (YJ) and Xuwen (XW) in Guangdong province were in the second cluster. The population from Heshan (HS) was nearer to the second cluster than the first. The second cluster was nearer to the populations from Haikou (HK) and Sanya (SY) than the other 3 populations, i.e. Qionghai (QH), Qiongzhong (QZ) and Danzhou (DZ) from Hainan Island. Combining the dendrogram analyses of characteristics of morphology and biomass distribution, can provide a theoretical basis for the study of pathways of E. catarium invading Hainan Island.