The invention discloses a method and a device for detecting abnormal network traffic data. The method comprises the steps of building a baseband model for detecting the abnormal network traffic data according to the preset detection cycle and historical data; determining the abnormality of the real-time traffic data according to the baseband model. With the adoption of the method, the technical support is provided to a user to adjust the network device measurement, and the detection accuracy of the abnormal network traffic data can be increased.