Abstract: Based on monthly surveys in the salt marshes of Chongming Dongtan in the Yangtze Estuary, we analyzed the distribution characteristics of macroinvertebrate functional groups and driving factors, especially exotic plants, along an elevation gradient. The results showed that dominant species varied across different elevations. Both omnivores and herbivores were dominant functional groups in the middle tiddal zone, while omnivores were dominant in the other sites. Both the abundance and biomass of each functional group significantly varied along the elevation gradient (P<0.01), and such variations differed for different functional groups. The abundance and biomass of carnivores in the lowest mudflat were significantly higher than those in the vegetated zones (P<0.05), while those of herbivores in the middle tidal zone, occupied by Scirpus mariqueter, were significantly higher than that in the other sites (P<0.05). Main habitat factors (including total phosphorus, total nitrogen, organic matter, available phosphorus, nitrate nitrogen, ammonium nitrogen contents and median-sized grain of the sediment), and shoot height and aboveground biomass of the vegetation, varied significantly along the elevation gradient (P<0.05), and the characteristics of those variations changed among different factors. The invasion of Spartina alterniflora did not change the dominant functional group in the high tidal zone, but increased the abundance and biomass of omnivores (P<0.05). Some environmental factors, including available phosphorus, nitrate nitrogen, ammonium nitrogen and organic matter of the sediment, were significantly different between invasive S. alterniflora and natural Phragmites australis zones (P<0.05). The variations of the composition and distribution of the benthic macroinvertebrate functional groups were determined by the combination of multiple environmental factors, while the main factors varied with groups. Nutrient content and salinity of the sediment were the most important factors driving the abundance and biomass of the functional groups, respectively. Therefore, it is necessary to consider the comprehensive effects of various environmental variables including hydrology, vegetation and sediment when we examine the distribution characteristics and underlying mechanism of functional groups of benthic macroinvertebrate.