To tackle the problems not having explicit semantics and powerful analysis ability of the traditional task decomposition and process modeling methods for airplane design in the cooperative development mode, an airplane general arrangement process modeling method based on task-related WBS and Petri nets is presented. On the basis of airplane system WBS, the TR-WBS model is built by using five constraint relations including optional, mandatory, choice, precedence, and feedback. By mapping the airplane general arrangement process model into a Petri net based model, the static structure description and dynamic analysis of airplane general arrangement design tasks is obtained, and the integration of the task decomposition and the process modeling is realized. The correctness, effectiveness and applicability of the method are verified through the established airplane general arrangement and coordination system.