The invention provides a system which can excavate the key information in a telephone natural dialogue, as well as a method thereof. The system comprises a telephone voice detection module, a voice keyword extraction module, a voice keyword database, a data excavation module and a user preference database which are connected sequentially, wherein, the voice keyword extraction module, the voice keyword database, the data excavation module and the user preference database are arranged in a computer; the telephone voice detection module is connected with a voice output device through a public switching telecommunication network (PSTN) or Internet. The invention can excavate the user's interests or data information such as the consumption demand, the consumption habit, the consumption field, the consumption category, etc. from the telephone voice, and create the user preference database, thereby can provide more reliable and more comprehensive and effective supports for an enterprise to make a marketing decision; the invention is applicable to a fixed telephone, a mobile telephone, a voice chat, etc., and has a wide business application prospect.