Abstract: Shrub encroachment is an universal phenomenon, which has become a global problem, and a hot issue in the study of global change ecology, grassland ecology, phenology, tourism and animal husbandry. It is defined as the increase of woody biomass, density and coverage, but the decrease of herbaceous biomass, density and coverage in grassland ecosystems. Shrub encroachment is the result of the interaction of overgrazing, fire and climate change. The shrub encroachment causes the change of grassland land patterns and biological patterns, which results in the fertile island effect, the change of grassland biodiversity and grassland productivity. In the future research, more work should be emphasized on the mechanisms of shrub encroachment, influences on the aboveground and belowground parts of grassland-shrub ecosystems and management approach of shrub encroachment, which is of great significance to the grassland production areas in China.