In this paper, we present a new way for researching the monotonous synchronization of chaotic systems in the complex networks. The method proposed here is based on the boundary and squeezing properties about Chen system. We study four complex networks, including ring network, star network, small-world network and globally coupled network, which all have N Chen systems. By theoretic inducing, we derive the sufficient conditions for synchronization, and prove that the small-world network is better than others by comparison. The result of numerical simulations is consistent with the theory.