Today's business enterprises must deal with global competition, reduce the cost of doing business, and rapidly develop new services and products. To address these requirements enterprises must constantly reconsider and optimize the way they do business and change their information systems and applications to support evolving business processes. Workflow technology facilitates these by the ability of handling complex transaction in heterogeneous environment to support (i) business process modeling to capture business processes as workflow specifications, (ii) business process reengineering to optimize specified processes, and (iii) workflow automation to generate workflow implementations from workflow specifications. However traditional workflow models which based on the "static" process definition lack of the necessary flexibility for the dynamic characters of contemporary business processes and thus they limit the application of workflow technology in wider area. In order to solve the deficiencies of the poor description ability, flexibility definition, reusable process and exception handling existed in existing workflow process model, this paper introduces the proposed methods based on an objected-oriented modeling technology, component method, coordination method, condition decision and multiple instances mechanisms extends the traditional activity network model. The new detailed modeling mechanisms and abundant activity definition properties are given in this paper, and experiment is presented in this paper too. Practical examples show compared with traditional activity network model, the proposed method has significant advantages like strong expressive power, flexible modeling methods and improving system flexibility and adaptability. The proposed method has important value in designing and developing workflow management systems with high reliable, flexibility and adaptability. Keyword: Workflow, Workflow Management System, Process Modeling, Meta-Model, Object-Oriented, State