Abstract: Using the soil moisture(volume water content)data of 50cm layer from 1991 to 2013 in all 31 agricultural climate sites in the southwestern karst region of China,to detailed analysis its temporal and spatial evolution characteristics by linear trend analysis and Empirical Orthogonal Function(EOF),further understanding the temporal and spatial evolution characteristics of soil moisture in karst areas of southwest China.The results show that, (1)There are obvious regional differences in the spatial size and distribution of the average mid-level soil moisture in the southwestern karst area have.(2)Analysising the seasonal average of mid-level soil moisture in 1991~2013,The soil moisture is the highest in autumn while it has the largest range of low values in Summer,it reflects the uniqueness of the soil in the southwestern karst region.(3).The interannual variation of mid-level soil moisture has obvious spatial distribution characteristics that"rising in South while reducing in North", the result of linear trend analysis and Empirical Orthogonal Function(EOF)also confirm this main feature.(4)The interannual variation of the mid-level soil moisture is relatively stable and the fluctuation trend is small, in general, soil moisture is highest in summer and autumn while lower in spring and winter.