Owing to increasing global terrorist activities, it is highly important to optitnize the allocation of a city's limited defensive resources to protect multiple chemical facilities against terrorist attacks. Considerable research has focused on assessing the risk of terrorist attacks on chemical facilities; however, conventional risk -based methods do not take into account the strategy adjustments of terrorists and cannot identify the optimal global allocation of defensive resources. This study presents a game -theoretic method for optimizing the allocation of defensive resources; it fully considers the strategic interactions between defenders and attackers by integrating game theory with risk assessment. As a case study, we tested the applicability and reliability of our method using eight chemical plants storing explosive materials in a city in China. In this way, we clarified the differences between conventional methods and our presented method; we confirmed the advantage of the presented method in identifying the optimal global allocation of defensive resources. (C) 2016 Published by Elsevier Ltd.