People are paying more attention on Intrusion detection which is an important computer network security technolog. However there are still many unresolved issues in Intrusion Detection, for instance, the rapid speed of network transmission and network high traffic flow lead to real-time and effectiveness detection going down, and can not detect complex and diverse intrusion. We are developing a new intrusion detection mechanism based on cloud computing. This mechanism uses a global view which can make up for the deficiency of traditional intrusion detection, and proved to be great scalable.