Emergency evacuation plan plays a key role for disaster management and successful evacuation. In this work, a conceptual decision support system is established and a method to determine the evacuation scope under toxicant leakage accidents is also proposed. Simultaneously, a route selection approach coupling with polluted scope is proposed based on operation mathematic analysis. The best route for evacuee at each location on toxic leakage accidents is the one along with which the heath injury is minimal. Hence, a variable based on toxic load is defined and noted as Dvi-vj, which is used to quantify the toxic exposure. The universally minimal Dvi-vj is taken as the optimized goal in the model. And then, one case is presented and indicates that this approach can aid the emergency managers to make the right response to the leakage accident in an efficient manner. This new method is also useful for fire risk assessment and design of chemical industrial park. (C) 2015 Elsevier Ltd. All rights reserved.