The advantage of COOZ (complete object-oriented Z) is to specify large scale so ftware, but it does not support refinement calculus. Thus its application is con fined and it can not be taken as a complete method for software development. I ncluding refinement calculus into COOZ remedies its disadvantage during design and implementation. The separation between the design and implementation for st ructure and notation is removed as well. Then the software can be developed smoo thly in the same frame. In this paper, development model is established, which i s based on COOZ and refinement calculus. Data refinement and operation refinemen t are debated with a example. As for implementary technology of refinement calcu lus, a data refinement calculator is constructed and an approach for data refi nement which is based on data refinement calculus and program window inference is provided.