Abstract: 20 plots were set in Alternanthera philoxeroides invaded regions in Xinyang city, using quantitative ecological techniques such as TWINSPAN classification and DCA sequencing to classify the association types and functional groups, as well as explore the relationships between functional groups diversity and A. philoxeroides invasion situation. The results showed that 20 plot communities were divided into 3 groups cluster type, A. philoxeroides+ Digitaria sanguinalis, A. philoxeroides + Echinochloa crusgalli and A. philoxeroides + Ophiopogon japonicas + Veronica polita. 78 plant species were divided into 3 functional groups, Gramineae group, Asteraceae group and other weeds group. Importance value of A. philoxeroides decreased significantly as total amounts of genera and species of accompanying plants increasing. With gramineae and compositae function group of this rise, 4 alpha species diversity indices of invaded community increased as species richness of Gramineae group and Asteraceae group increasing, and the positive effect of Gramineae group on species diversity was higher than that of Asteraceae group.