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.