Shrub encroachment can change the ecosystem structure and function, even lead to the degradation or desertification of arid or semiarid grassland. This review comprehensively analyzed the impacts of precipitation, air temperature, soil character, biotic factor and human activities on shrub encroachment, and summarized the influences of shrub encroachment on ecosystem as well as the effective control measures against shrub encroachment. The increasing amount and distribution pattern change of precipitation generally facilitate the shrub encroachment. The global warming can alleviate the freeze injury to the shrub, and then decrease its mortality rate, which is favorable to the expansion of the shrub. Due to high adaption ability of shrub species, the land degradation and over-grazing can also facilitate shrub encroachment. Appropriate frequency of fire can suppress the shrub encroachment. Shrub encroachment is often associated with lower pasture value of the grassland, as well as changes of soil moisture and nutrient pattern, but has different impacts on grassland biodiversity and biomass. There are some effective control measures on shrub encroachment including reducing anthropogenic disturbance, applying adequate fire and artificially removing shrub. To improve the effectiveness of shrub encroachment control, a combination of several measures should be applied according to the specif?ic environment. Presently, the study results of shrub encroachment were mostly based on observation in field study without supporting data from big-scale and long-term field experiments. Therefore, further study on the process of shrub encroachment is needed. Besides, there are no consistent conclusions on whether the shrub encroachment process can be reversed as well as how it can be reversed. Although research on shrub encroachment just started in China, the phenomenon has happened long time ago in the grassland of this country. Thus, comparative studies between China and other regions can help clarifying the formation mechanisms and process of shrub encroachment.