A typical catchment named Tongshuang small watershed,which was subjected to drastic erosion before 1980 and was managed subtly after 1980 in black soil region,was chosen as a study area.The data of soil bulk density,topographic factors and land types were obtained by soil sampling and measurements,deriving from DEM and remote sensing image,respectively.Classical statistics and geostatistics analysis methods were used to describe the spatial variability and to explore the correlation of topographic factors and land use with soil bulk density.The classical statistics analysis results indicated that the soil bulk density of study area was moderately variable(C_v=14%).The slope position and land use were the most discriminating influencing factors.The geostatistics analysis showed that soil bulk density had similarly moderate spatial correlations. The spatial correlations were mainly induced by stochastic factors(C_0/C_0 C=41.18%).The effective spatial autocorrelation range was(2 402) m.The control of soil erosion was successful and inspiring.However,of whole farmland,48.3% was worrisome for their surface's soil structure.It will be an impending task to improve soil fertility.