Abstract: The lack in representing the relation between activities with Boolean Design Structure Matrix (DSM) is analysed, and task load and time model is also presented by introducing Task Transition Matrix (TTM) in this paper. Based on the model, we study the law of the repetition and overlay caused by coupled tasks in design process in order to identify the chief factor—design drive, which affects design process strongly. This can help implement Concurrent Design, which can be extremely complex and systematic because of the integration among multi-domains.