Abstract: Interactions among wetland plants mainly include competition (negative effect) and facilitation (positive effect), which are the primary content of wetland ecology. Plant-plant interactions also play an important role in determining plant distribution and in regulating the composition of community or ecosystem. This paper describes the theories of competition and the main factors affecting competition ability of wetland plants, introduces the concept of facilitation and its formation mechanism in wetland ecosystems, and discusses the theory about the shift of plantplant interaction and the main environmental factors (water level, temperature, salinity, biotic factors) influencing the shift of plant-plant interaction. With the increase of stress intensity, plantplant interaction generally shifts from competition to facilitation, that is, competition usually occurs in favorable environments while facilitation dominates under stress conditions. Currently, many studies have been performed in coastal salt marsh ecosystems and the studied ecosystem type is incomprehensive, therefore, research efforts should be expanded to other wetland ecosystems, such as freshwater and estuary wetlands. Meanwhile, studies on biological mechanisms and time-dependent effects
 on the shift of plantplant interaction, the exploration of new methodology should be strengthened in the future, which will be helpful to understand the mech
anisms on the formation and shift of competition and facilitation among wetland plants.

Key words: Myzus persicae, Erigonidium graminicola, Spatial structure, Models