Abstract: This paper studies the dynamic of the Chinese grasland resource in different aridity areas supported by GIS and RS based on TM images ．The results show that there is an obvious zone under different aridities where the high cover grassland is changed to farm land especially at 4，5，6 degrees which are mainly distributed in the west and north of China and in these zone the grasland is being replaced by urban at each aridity area and the grasland is being degradated．The area between the grasland changing into farmland and farm land changing into grasland is about the same in middle cover grasland，but the area occupied by the farm land shows that the grasland decrea ses and a lot of grassland are changed into forest．With the increasing aridity degree，the degradation becomes serious in low cover grasland，especially at 4，5 degrees ．But at 1 degree，the main change is that the grasland is changed to forest．The main reasons of grasland changing into farm land are the population pressure and over graze，etc. Grassland degradation will lead to the environment of north China worsen．