Objectives: Calcium is a major component of the karst environment and is one of the key elements in determining the structure and function of karst ecosystems. The relationship between soil organic carbon and pH and calcium species in the karst area is unclear. Methods: The natural vegetation soil was collected at a period of three months in Guilin Yaji karst test site for two years. The calcium species was studied by Bureau Communautaire de Référence (BCR) method. Results: The results showed that: （1） the content of extractable calcium is the highest, with an average of 61.63% of total calcium content. It shows that calcium in limestone soil has active migration, biological action, and high activity. The order of the contents of calcium species from many to less is extractable calcium (61.63%), reducible calcium (19.68%), residual calcium (13.92%) and oxidizable calcium(OCa) (4.77%). (2) There was a significant positive correlation between the calcium species and soil organic carbon (P <0.01) , except that the correlation between oxidizable calcium and soil organic carbon was not significant (P>0.05). And the relationship between pH value and calcium species was similar to that of soil organic carbon. (3) The relationship between calcium and organic carbon and pH was sorted by Redundancy Analysis (RDA). The order of relationship between calcium and organic carbon and pH was as follows: reducible calcium>extractable calcium> residual calcium> oxidizable calcium. Conclusions: The results of the study will help us to understand the distribution and movement characteristics of calcium in karst ecosystem, and provide the basic data for deep understanding of calcium cycle in karst area.