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Karst dynamic system operation mainly includes carbonate rock formation and its dissolution and weathering.The carbonate rocks' formation made great contribution to atmospheric CO2 sink in geological age,as the result of the processes,the concentration of CO2 reduced from over 25%in primitive atmosphere of ancient earth to only 0.03–0.04%in modern atmosphere.The carbon stored in carbonate rocks,which amounts to 61×1015 t,is known as the largest carbon pool on modern earth,representing 99.55%of the global carbon storage.In modern karst dynamic system,there evidences show the carbonate rock dissolution and weathering actively involves in the global carbon cycle,and sensitively responds to climate and environmental changes,the annual carbon sink flux derived from carbonate rock dissolution amounts to 0.36–0.44 PgC/a,which is close to the figure of 0.477 PgC/a,accounting for 32.73–40.00%of global forest carbon sink of 1.1 PgC/a from 1990 to 2007.This figure equals 45.00–55.00%of net carbon flux for global soil organic carbon pool under appropriate management.Finally,this paper gave the conceptual model of Karst Carbon Cycle in Watershed,consisting of three parts: carbonate rocks dissolution removing the atmospheric/soil CO2 to water and to produce inorganic carbon ; inorganic carbon transfer and conversion along with water flow ; inter-conversion between inorganic carbon and organic carbon with the aquatic plants photosynthesis,part of the organic carbon deposit on the river/lake/reservoir beds mixing with sediments.