It is very important to study Large Scale Networks Intrusion Detection and Warning System(LSNIDWS), which can increase the network systems reaction ability to catastrophe, slow down the harm of the network attack, enhance system counterattack ability.The summarization of studying situation in the world is first presented. Then, the structure and its component of LSNIDWS are presented.Finally, the key technology and difficulties related to building LSNIDWS prototype are discussed.