Abstract: According to the data collected from ten typical plots in Zhejiang Province,we analyzed the diversity of the communities invaded by alien plant Spermacoce latifolia using species richness index,Simpon Index,Shanon-Wiener Index and Pielou Index.In order to test its competition,relative association,and the position with other species in the communities,the niche breadths,niche overlaps,multi-interspecies association,and pair-interspecies association of S.latifolia with other 20 species were determined.The results were as follows:(1) The diversity of the communities decreased with the invasion of S.latifolia;(2) The widest in niche breath of S.latifolia dropped a hint that it could survive in any environments and easily compete with other species in the community;(3) S.latifolia had greatest niche overlaps with Digitaria ciliaris,followed by those with Conyza bonariensis and Cyperus rotundus;(4) The χ2 analysis indicated that no species in the community had a significant relationship with S.latifolia,which only had a positive relationship with D.ciliaris,C.bonariensis and a negative relationship with C.rotundus,Commelina communis and Lindernia crustacea.