Abstract: The paleokarst investigation plays more and more important role in the field of petroleum exploitation. Great amount of work on the paleokarst investigation has been and is being done by many experts. After amounts of relevant articles have been consulted, together with what has been done by the author, the paleokarst is re-defined. Then the article makes a comprehension about the methods used by the native and foreign experts. The advantages and disadvantages are discussed and then the suggestion on the future studying ideas and methods is provided.