Red bare soil is a kind of the paleosol remained in the plateau surface influenced by the ancient climate. The study analyzed the stability and influential factors of the surface-layer soil aggregates in 14 typical samples of paleosol. The results showed that: 1) on the basis of international standard partition, the red bare soil generally belonged to silty clay in texture; 2) the indices of WR_0.25 ranged from 28.77% to 52.87%, PAD from 34.28% to 68.10%, MWD from 0.51 to 1 mm, GMD 0.37 to 0.58 mm, and FD from 2.79 to 2.92, respectively, all the above parameters reflected red bare soil are poor in structural stability, anti-erodibility and physical property when compared with other typical soils in southwest karst area of China; 3) soil orgnic matter played a more important role in deciding water stability of read bare soil aggregates than clays. Long-term bareness and soil orgnic matter shortage deteriorate soil structure stability, led to severe soil erosion and hinder vegetation restoration in red bare soil area.