Workflow process modeling is a complicated and error-prone procedure. It is highly noted in both research and industrial area that the cost for modifying errors is very high after a process definition becomes operational. Thus, effective process verification in modeling phase is very essential. This paper summarizes the state of the art of workflow process verification. Firstly, importance of verification is emphasized, then depiction of problems needed to be verified and their complexities are stated, next the requirements for verification methods are described. After introduction of these essential problems, two sorts of important verification techniques are discussed in detail. The first one is soundness verification, whose research results on Petri net model are presented. The second one is reduction verification, whose research results on Petri net and workflow graph are given. Besides, other verification methods, including correctness verification and those methods based on LTS or UML, etc. are simply mentioned. By analysis and comparison, the problems may be researched and future trends are finally presented.