Port hopping is a new type of information hiding technology emerged in recent years,and it has very prosperous development and application prospect in the network covert communication.The port hopping technology features the non-fixed sending and receiving ports,which hop randomly and simultaneously in communication.Compared to the traditional communication with fixed port,the communication using the port hopping technology makes it difficult to discover the port of communication,and even if the port is discovered by the enemy,the communication has already been transferred to another port.Therefore the port hopping is more covert than the traditional technology,and communication using it is difficult to be intercepted.This paper analyzes the basic principles and key technologies of the port hopping,carries on modeling analysis on the port hopping process,and assesses theoretically the system security through the models of the port security,the system availability and the system confidentiality.On this basis,by the use of Windows Sockets technology and VC+ + programming,it designs and implements the session-based port hopping system.Experiment results show that the system successfully makes the data packets diffuse in the background noise of network through the port hopping technology,and effectively reduces the hacker attacks in view of the specific port.At the same time the viability of the system is improved compared with that of the fixed port system.