Internet traffic classification plays an important role in network management,and many approaches have been proposed to classify different kinds of internet traffics.A novel approach was proposed to classify network applications by optimized back-propagation (BP) neural network.Particle swarm optimization (PSO) algorithm was used to optimize the BP neural network.And in order to increase the identification performance,wavelet packet decomposition (WPD) was used to extract several hidden features from the time-frequency information of network traffic.The experimental results show that the average classification accuracy of various network applications can reach 97％.Moreover,this approach optimized by BP neural network takes 50％ of the training time compared with the traditional neural network.