This paper addresses the decomposition of network systems for distributed control. We construct a novel weighted input-output bipartite graph representation of control systems, in which the input-output edge weights capture topological connectivity and short-time response sensitivities. We then introduce community detection as a network-theoretic tool to generate a decomposition with strong intra-subsystem interactions and weak inter-subsystem interactions. A modularity-based graph bisection procedure is applied recursively to determine the optimal decomposition. The proposed method is applied to a chemical process network example. (C) 2018 Elsevier Ltd. All rights reserved.