Conclude the current anomaly network flow detection methods for the anomaly network flow problem in network environment. By introducing key problem and key technology of network anomaly flow detection, pay more attention on discussing principle and application area of constant-threshold, feature detection, statistical analysis, data mining, and cloud computing method. Conclude definition and classification of network anomaly flow, introduce related research, and carry out further analysis current situation and development prospect of anomaly flow. The analysis result provides a reference for the detection of anomaly network flow, and also provides support for network security research.