The physical property of karst mountain desertification soil under different land use in Chongqing Beipei karst mountain was studied. The result shows that when the nature forest land is replaced by grass land

artificial land

vegetable land and plantation gradually

the land is becoming more arenaceous and the soil bulk density in- creases

and the total percentage of pore

especial the percentage of non-pore increase greatly. Although the ag- gregate structure measured by dry sieve are quiet similar under different land use

the water-stable aggregate structure got by dump sieve is quite different. The destroy of aggregate structure is high. With the vegetable land and plantation changed into deserted land

all physical standards are improved. On the basis of those studies

the author briefly analyzed the correlation between the degrading soil physical feature and the desertification

and pos- sibility of reducing the soil erosion by deserting land.