Provides methods for transforming a flowchart to an equivalent tree diagram, methods for transforming an equivalent tree diagram to a flowchart, methods for verifying reorganization of a flowchart, methods for editing a flowchart, methods for creating a flowchart and a flowchart editor. A flowchart includes one or more logic structures and one or more processing activities in said one or more logic structures. The method for transforming a flowchart to an equivalent tree diagram comprises: traversing said flowchart; transforming said one or more logic structures in said flowchart to one or more branching nodes in said tree diagram; and transforming one or more processing activities in said logic structures of said flowchart to one or more leaf nodes below corresponding branching nodes in said tree diagram. Further, edition of a flowchart and verification of reorganization of a flowchart are performed by utilizing an equivalent tree diagram.