Because of its attractive cost and yield, hierarchical assembly, in which constituent structures of lower hierarchy share a majority of components, is an appealing approach to scale up DNA self-assembly. A few strategies have already been investigated to combine preformed DNA nanostructures. In this study, we present a new hierarchical assembly method based on four-way toehold-mediated strand displacement to facilitate the combination of preformed DNA structural units. Employing such a method, we have constructed a series of higher-order structures composed of 5, 7, 9, 11, 13, and 15 preformed units respectively.