The process of vegetation restoration and succession had improved soil obviously in degenerated ecological system especially soil physical characteristics in series of succession stage in naqu county North Tibet are investigated here;and ratio on soil grain composition in series succession stage are analyzed;meanwhile,soil bulk density and porosity are measured.The correlation analysis between soil physical characteristics such as soil grain composition,soil bulk density and porosity and soil succession stage are made in this paper,and then a inherent concern between succession stage of degraded grassland and the change of soil physical characteristics in this region are probed.(1)Trample makes the soil expose,that cause the function of corroding to aggravate;loose sand grain and slit that does not cohere had lost heavily,but the lost of grain which smaller than 0.02 mm and cohesive soil was relatively less,so that it was demonstrated percentage to be relative to increase strong directly;As a result,trample had changed the normal structure of the original soil,and influenced on the soil physical properties badly along the line of the highway,and impel the land to be further degradative.(2)With the process of restoration,the top layer soil total porosity increases,and bulk density is reduced,above all relevant with the series succession stage prominently;With improvement of aeration,infiltration and drainage percent,the availability of moisture soil increases corresponsively.