This paper addresses the issue of security coordination control for belt conveyor systems (BCSs) vulnerable to false data injection (FDI) attacks in an industrial Internet of Things scenario. A networked BCSs drive model is established for the first time consisting of flexibly connected dual permanent magnet synchronous motors. Subsequently, a novel security control strategy based on quadratic regulators is proposed to preserve the drive motor synchronization in response to FDI attacks that compromise the signal interaction from sensors to controllers. Afterward, a composite sub-optimal security coordination controller is presented based on the singular perturbation theory and the corresponding solution approach, recognizing the two-time-scale dynamics inherent to motor systems. The proposed criteria both eliminate ill-conditioned numerical issues and assure system stability. Furthermore, simulations exhibit the advantages and physical experiments confirm the efficiency of the developed algorithms.