The three networks convergence is a main direction of network development, and wireless networks will mainly serve as a means of access to the wire-line networks. This paper mainly describes in outline the present technological condition of the Internet, telecommunications networks, cable TV networks, and wireless networks, analyses respectively from a view of the trend of the three networks convergence their capability to provide the core technologies that can be used to develop future integrated service networks that can provide all of the services now provided by the three types of networks. It is pointed out that no single network technology will emerge as the undisputed winner, the converged networks will be characterized by a collection of heterogeneous networks which offer a variety of services. Finally, the paper takes a broader perspective, presents the characteristics of the future global multimedia network that will be seen after the three networks convergence, the challenges that will be confronted with by the researchers and the needed innovations to build the network with these characteristics.