1. A flowchart editor comprising: a computing device performing: traversing the flowchart, wherein said flowchart comprises a main processing flow, a logic structure within said main processing flow, and a processing activity in said logic structure; and forming an equivalent tree diagram corresponding to the main processing flow of the flowchart by performing steps of: transforming the logic structure in the flowchart to a sub tree comprising a branching node in the equivalent tree diagram; assembling the sub tree to the equivalent tree diagram; transforming a task required by the processing activity to a leaf node below the branching node in the sub tree; and decomposing the task represented by the leaf node to a least one sub task and setting each sub task as a child leaf node below the leaf node; modifying the leaf node to a sub-branching node of a type corresponding to an execution logic of the at least one sub task, wherein the execution logic comprises a loop logic structure and at least one of: a sequence logic structure and a split logic structure; repeating the decomposing and modifying steps until the tasks represented by all the leaf nodes in the equivalent tree diagram cannot be further decomposed; and further comprising an equivalent tree diagram editing unit performing: selecting at least one node in the flowchart for editing; executing the editing of the flowchart; using a reorganization verifying unit for verifying validity of the editing, comprising: determining that the editing is valid when the at least one node in the flowchart corresponds to a sub tree in the equivalent tree diagram; and determining that the editing is valid when the at least one node in the flowchart corresponds to a plurality of sub trees in the equivalent tree diagram and said plurality of sub trees have a same parent node in common.