The invention discloses a network flow classifying system and a network flow classifying method combining a DPI and a DFI. The network flow classifying system is formed by combining a DPI service recognizing system module and a DFI flow recognizing system module, wherein the DPI module comprises a flow meter detecting module and a flow recognizing module; and the DFI module comprises a sample acquiring module, a classifier training module and a classifier classifying and predicting module. The sample acquiring module divides data stream capable of being accurately recognized by the flow recognizing module in the DPI into several classes and adopts the data stream as a sample to train the classifier training module so as to acquire a classifying model which can distinguish the class of thenetwork flow; then the flow which can not be recognized by the flow recognizing module of the DPI passes through the classifier classifying and predicting module of the DFI so as to achieve the aim for distinguishing the class of the flow which can not be recognized by the DPI. The invention is more comprehensive than a method for singly using the DPI or the DFI and can accurately recognize a service which is not encrypted in an application layer and distinguish the class of the service which is encrypted in the application layer.