The karst region of south China is a fragile eco-region where rocky desertification is widespread. Taking karst mountain area of north Guangdong for example, we studied the process of land rocky desertification with the methods of site investigations, station-oriented observations and simulated tests from the perspective of land surface ecological processes. In the process of rocky desertification developing from light to extremely serious, vegetation of that is degenerated from shrubby and herbaceous mixed community to herbaceous community, and species is reduced by 76%, Coverage of vegetation is decreased by 87.2%, soil erosion is aggravated, soil material is losing continuously and soil layer is getting thinner, therefore, modulus of erosion has increased by ten times even dozens of times. Rocky desertification land has special hydrological process and water cycle model. With the aggravation of rocky desertification, more and more surface water and ground water is lost, and the pulsed growth rate of limestone in soil is faster, so that the rate of outcropping bedrock has increased from 30%—50% to more than 90%, eventually leads to soil coarsening, nutrients loss, and 89% or even more reduction of biological production. It shows that land rocky desertification is a process of land degradation, which includes the process of vegetation degradation and loss, soil erosion, surface water loss, carbonate rock corrosion and erosion, and biological productivity of land degradation, meanwhile, it is an evolving process from Karst mountainous area land ecosystems to rocky desert systems.