This paper investigates the decentralized control for a large-scale system with an IP-based communication network. The decentralized controller design specifically takes the nonuniform communication-delay-distribution characteristic of the IP-based communication network into account. First, a networked decentralized control modeling for the large-scale system is proposed. The two main points are: 1) a decentralized controller is designed, which does not depend on the full-order state of the system and 2) the nonuniform communication-delay-distribution characteristic of the IP-based communication network is fully considered in the controller design. Second, if the probability distribution of communication delay is known a priori in the design process, sufficient stability and stabilization conditions for the networked large-scale system are derived in terms of linear matrix inequalities. It shows that, the solvability of the design depends not only on the probability distribution of the communication delay but also on the network topology. Finally, the design method is applied to two pendulums coupled by a spring and a quadruple-tank process. Simulation results demonstrate the effectiveness of the proposed method.