In recent years, electric vehicles (EVs) have been widely accepted by general publics due to their low emissions. Particularly, those EVs which are able to be connected to power grid have earned lots of attention. In this paper, a multilayer framework is newly proposed for vehicle-to-grid operation and cost-emission analysis is carried out based on this framework. Hence, operation cost and emissions can be reduced by using these gridable EVs. The key is to introduce particle swarm optimization to find out the optimal scheduling of generating units and gridable EVs.