Abstract:The research on the effect of grazing on physiological action of herbage plays an important role in probe into the physiological mechanism of succession in grazing grassland.Many results showed that the effect of grazing on photosynthesis respiration,absorption and transportation of nitrogen and carbon in herbage could be significantly divided into two stages,including physiological injury and regularization.The changed structure of canopy by grazing resulted in a variation of canopy photosynthesis.The net photosynthetic rate was sharply decreased in short period,and then gradually getting back with the increase of leaf area.The response of respiration to grazing was similar to that of photosynthesis.Nitrogen and carbon used in the revegetation chiefly came from the stored matter in root and stubble at the first period after grazing.Then,the assimilation met the need of revegetation to use nitrogen and carbon with the recovery of physiological action.The absorption and transportation of carbon after grazing was negative relationship with the nitrogen level in soils.The effect of grazing on the physiological processes of herbage had a close relationship with the genetic characteristics of herbage,inter-specific competition,grazing characteristics of livestock,and environmentally abiotic factors such as light,heat,water and soil.