Disclosed in the present invention are a volume measurement system and method for a closed water-filled karst cave, comprising a water collecting device, a concentration tester, and a control system, wherein the control system is connected to the water collecting device by means of a connector, the water collecting device is a container having a closed top portion and an open bottom portion, the top portion of the water collecting device is a piston, the piston is connected to a propulsion rod, and the propulsion rod is controlled by the control system to extend or shorten to thereby achieve the advancement or retreat of the piston; a placing table that may be opened and closed is hinged at an inner wall of the water collecting device, and the placing table is connected to the piston; when the piston is raised, the placing table moves upward, and when the piston is lowered, the placing table moves downward; the placing table is used for the placement of a chemical substance thereon; and the concentration tester communicates with a lower portion of the water collecting device and is used to detect the concentration of a solution.