This paper considers networked active vibration control for structural systems with multiple degrees of freedom. For the structural system suffering from an earthquake stimulation, a networked negative velocity feedback controller (NVFC) is constructed to implement the vibration control. By considering network-induced delay, the resulting system model of the networked structural system is established as a system with a time-varying delay. A new H∞ performance criterion and a controller designing scheme are derived by a complete Lyapunov-Krasovskii functional (LKF) with the partition of the delay bound. Simulation results show that the proposed design method can improve the vibration control performance and the designed networked NVFC can fulfill a superior vibration suppression effect with smaller control force.