Abstract: Weeds species and distribution were investigated by sampling method in different habitats of the coastal region in the south-east of the Fujian province, where Eupatorium catatium has existed. Species diversity of the weeds community including E. catatium, niche breath and niche overlap of 23 main kinds of weeds was analyzed by applying the species richness index(S), Simpson's Index(Ds), Shannon-Wiener Index(H')and Pielou evenness indice(J). Meanwhile, effects of E.catatium on weeds community composition and species diversity were also investigated.Results suggested that fifty-eight weed species belonged to twenty-two families exist with E.catatium and twenty of which were alien. Furthermore, sixteen of twenty belonged to the asteraceae family and nine of which were alien.E.catatium had stronger ability to adapt to the environment and more competitive for it had broader niche breadth than the other species of weeds in the community.Results also indicated that Solanum nigrum and Acalypha australis shared the largest niche overlap, and E. catatium and Conyza canadensis were followed.