Machine learning with C4.5 algorithm is proposed for network traffic identification. The correlation feature selection algorithm and the genetic algorithm are adopted to select the attribute feature subset. A method of combining N-fold cross-validation with testing set is suggested to assess the classification results of the current national broadband network traffic. Experiments demonstrate that network traffic can be successfully identified and analyzed, meanwhile, the port number and the application layer protocol label of network flows are not necessary to be known in advance.