The carbonate rock area in the Chenqi village of Puding County, Guizhou Province is an area of karst rocky desertification. This paper examines the stability of brown clayey soil in the karst rocky desertification. The paper uses the wet sieving method. The results show that cracking of the brown clayey soil aggregates due to encountering water occurs in the early soaked stage. The less the initial water content of the brown clayey soil aggregates is, after soaked with rainwater, the quicker the cracking of soil aggregates is. Stability of the brown clayed soil aggregates is good for the soil with high water content. So, for prevention of rocky desertification of the carbonate rock area, it is important to take into consideration of the effect of desiccation climate and evaporation quantity on the soil loss.