Signatures responsible for authentication, authorization, etc, are important in many workflow applications. Most studies associated with signatures are focused on digital signatures only, and modeling of signature workflows is seldom studied. However, the dependencies between signatures can be complex, and thus modeling signature workflows becomes time consuming and error-prone. In this paper, we propose six patterns to simplify the design of signature workflows. AU the patterns are described in BPMN and a case study is made to illustrate how to apply these patterns in construction of a workflow. A method for applying these patterns in development of workflows is sketched, and the advantages, simplifying the construction of a workflow with BPMN, are also revealed with the case study.