A dual stack mobile communication system is provided for building a single interworking network of an asynchronous network and a synchronous network. A single node is formed by combining the same kind nodes of the asynchronous network and the synchronous network, wherein the single node searches information for generating two output signal points according to a synchronous protocol and an asynchronous protocol in one input signal point according to the synchronous protocol or asynchronous protocol, and generates one output signal point.