Instant Message is currently the most popular way to communicate on the Internet, so various Instant Messaging software are continuously appearing; Service providers offer more and more communication service nowadays. Java programming language (Java 2 Standard Edition) is one of popular programming languages. With its features of cross-platform, security, multi-threaded capability, Socket Programming, data flow concepts and so on, Java has its own distinctive and functional advantages. Therefore, based on the research and analysis of LinuxQQ, with the Java language and J2EE, this paper designs an instant messenger—JICQ (Java for I seek you), and then analyzes its architecture, modules, as well as its key technologies. During the design and modeling process of instant messenger system, the UML and method of object-oriented analysis and design are used. Furthermore, the modeling tool of Rose is included. Based on the system j2se1.5, j2ee1.4, the Eclipse development tool in the development process, and refactoring development method, the system design is optimized. Due to these factors, the system is safe, efficient and practical in different operating system platforms.