Abstract: Southwest karst area is one of the main karst zones in China and also the research focus in the world. Large population and heavy environmental pressure have seriously destroyed the vegetation in the research region and even brought about a series of environmental problems due to human activities in some areas. In this paper, based on the vegetation succession principle in the karst area, the authors studied the different vegetation habitats and analyzed the karst effect of vegetation in the karst area, especially in the epikarst area, by comparing the hydrochemical characteristics in diverse epikarst springs and the content of CO2 in surficial layer soil.Here are some conclusions drawn from the study: (1) In the Southwest karst area, different vegetation coverages result in different contents of CO2 in surficial soil and different chemical powers. Thus the dissolubilities are different. The higher the vegetation coverage, the higher the carbon dioxide content and the stronger the dissolubility of soil solution to carbonate rock. (2) Soils of different vegetation coverages have different water retention capacities.In general, in areas with higher vegetation coverage the water retention and fertilizer-holding capacity is stronger due to the effect of root system and litter layer.As a result, physicochemical reaction occurs between soil solutions more completely for a longer time. For example, the average content of HCO-3 in the epikarst spring in Yajicun (Guilin) covered mainly with bush is 5.56 mmol/L,whereas the average content of HCO-3in epikarst spring in Meihuashan (Liupanshui) covered mainly with grass is only 3.25 mmol/L. (3) As presented in many references, vegetation can improve water and soil retention, which is important to the karst area with a fragile environment. On the one hand, barely poor soil can be kept to provide vegetation with necessary nutrient and water resource. On the other hand, improving dissolubility can enhance soil formation in the karst area. (4) From what is discussed above we know the effect of vegetation plays an important role in ecological recovery of the karst area,especially of bare or semi-bare karst areas. Therefore, we should forbid deforesting, mountain firing and overgrazing. If conditions are ripe,we should resort to a series of means to recover vegetation and ensure its positive succession to improve the ecological recovery in karst areas. The research into the karst effect of vegetation in karst area shows that the karst study can be promoted. In addition, we can increase the karst environmental protection consciousness in people's mind and provide basic material for ecological recovery in Southwest area.