Researches on complex networks have been performed across several fields of science, including technical networks, information networks, biological networks and social networks. Researchers have discovered different types of characteristics for complex networks such as regular-coupled networks, random networks, small-world networks and scale-free networks. Application of such network properties to solve real network problems, however, is still at the infancy stage. In this study, some key characteristics of complex networks are critically evaluated, the current state of complex networks and the application of theories of complex network to real network design. In particular, inspired by the average-path-length property and clustering coefficient, they are employed to evaluate the theories. It will also identify some of the challenges in applying these theories to real networks.