A method and an apparatus for notifying a network abnormality are provided. An OpenFlow switch detects whether an abnormality occurs in an OpenFlow network. The OpenFlow switch sends a first asynchronous message for describing the abnormality occurring in the OpenFlow network to a controller when detecting an abnormality occurring in the OpenFlow network, so that the controller processes, according to the first asynchronous message, the abnormality occurring in the OpenFlow network. In this way, the abnormality in the network is notified in time, thereby improving efficiency in processing the abnormality in the OpenFlow network. A technical problem in the prior art that an abnormality occurring in an OpenFlow network and caused by an unexpected event cannot be notified in time, so that the abnormality occurring in the OpenFlow network cannot be processed in time and efficiency in processing the abnormality occurring in the OpenFlow network is relatively low is solved.