The invention provides a flow detection system and a flow detection method for a virtualization environment; the system comprises an agent module, an abnormal flow detection module and a control module, wherein virtual machine flow matched in a flow table are forwarded directly via a virtual switch, and the virtual machine flow unmatched in the flow table are sent to the abnormal flow detection module and update a virtual switch flow table; for the virtual machine flow with a normal detection result, flow table items are added at the flow table place so as to allow the virtual machine flow to pass; for the virtual machine flow with an abnormal detection result, the flow table items are modified and access control is set to block virtual machines with the abnormal flow; and the control module decides to-be-blocked physical machine connection with the abnormal flow or physical machines to be listed to a blacklist, and updates a physical switch flow table. The system and the method disclosed by the invention can detect the abnormal flow among the virtual machines, among the physical machines and among the virtual machines and the physical machines, are more adaptive to requirements on magnanimity, real-time detection and the like of the flow, and can carry out more comprehensive detection on virtualization flow.