Research conclusions: Bedding detachment and longitudinal tension fractures located at core and eastern wing of the Maoba syncline cutting by transverse tension fractures（NW~NWW)，form the initial space and route way , which are the passage the deep cycle of karst aquifer. A type of deep flow cycle named inverse siphon cycle forms. The flow water dissolves the carbonate rocks along the route way. Conduits are formed by perennial corrosion of the water. The great cave forms due to corrosion and collapse of ceiling the cave. The cave is filled by clayey soil，which deposits due to the changes of the flow.