A Java chip operating system (JCOS) is presented in this paper, which is an object-oriented operating system for embedded applications based on Java chip. JCOS is composed of three kinds of components including severs, kernel and transition layers. The model of JCOSis constituted by the abstract characteristics of these components. The specific components inherit above characteristics and specialize their features. By this technology, JCOS is developed and maintained easily, and has better scalability, portability,portability and code reuse ability.Architecture,model and implementation of JCOS are introduced in this paper.At last,JCOS iscompared with som related work.