Along with the rapid development of science and technology and the growth and popularization of internet, instant message plays an important role in the people daily communication. In campus network, instant message becomes more and more popular as a convenient and effective means of communication except tranditional methods like Email. Now the XMPP is in people's spotlight and becomes official standards of instant message, so the research of the instant message dedicated to campus network based on XMPP is very valuable and useful.Up to now, it is very rare of the instant message system dedicated to campus network, so most of the solutions utilize the personal instant message system instead. It is very difficult to communicate with each other since these softwares'protocols are private. The instant message system dedicated to campus network must support the uniform identity authentication via the same authentication source existing in its infrastructure. In order to improve user's experience of searching information and communication with each other, the instant message system dedicated to campus network replace tranditional buddy list with social hierarchical tree.In the premise of well understanding of protocol XMPP, Kerberos and LDAP, we design and implement the instant system dedicated to campus network. To achieve better coupling between system's modules, we make use of hierarchical design to implement data storage subsystem, authentication subsystem and user interactive subsystem. The module of user interface is implemented by Python programming language and the infrastructure by C programming language. At the end of this paper, we put in some suggestions of how to improve the system, which would contribute some information for implementing instant message system dedicated to campus network.