Abstract: To make workflow processes more flexible, a dynamic generation approach for workflow processes corresponding to an instance is presented in this study. An activity, a part of a workflow, is defined as an action based on Description Logics (DLs). User preferences are considered, since a final solution should satisfy user preferences as much as possible. Also, a hierarchical workflow ontology model is proposed and a deciding method for basic routing relations in workflows is provided to produce the processes completely. Then for generating the processes, a new planning algorithm of workflow processes, DPWPG: Dynamic Planning for Workflow Process Generation, is presented and used to search matching activities in a workflow ontology model, according to ontological reasoning in semantic activities and users’ preferences. Finally, an example is given to test the performance of the planning algorithm.