Abstract With intensive mining of groundwater and expansion of irrigation area, reversion has happened to the grassland and arable area of West Liaohe River Plain, and the natural property of ecological system has declined sharply. Through historical literature research and plant sampling survey, comparison was made for the status dynamic change of grassland vegetation community on the West Liaohe River Plain before (1980) and after interference (2016). According to the result, it showed that the grassland vegetation species diversity of West Liaohe River Plain dropped from 917 to 258. Besides, the influence factors affecting vegetation community change were also analyzed, 1) the grassland was occupied by arable land, thus resulting in a shrink in grassland area from 48, 900 km² in 1980 to 22, 400 km² in 2016. Due to the locality in species distribution, therefore, the shrinking process of grassland also represented the process of species disappearance; 2) large-scale well irrigation resulted in the overall decrease of underground water level and the vegetation ecological degradation; 3) overgrazing and other problems brought by rapid development of animal husbandry.