Abstract: A maximal coverage location model based on network Voronoi area diagrams and particle swam optimization are proposed, which have been applied to spatial optimization for time sensibility public service facilities in city. In this paper we take that facilities function radiate to the areas along traffic network and variable demands continuous distribution into account, the sites of facilities optimized can be located in continuous network space. The network Voronoi area diagrams were used to simulate the service areas of facilities in the maximal coverage location model, which has heuristic to minimize overlap coverage in spatial optimization. The model proposed maximizes comprehensive utilization of facilities, which formulates that the demands within a certain distance from at least one facility are provided complete service coverage and the demands beyond the distance from at least one facility are provided partial coverage. An improved Particle Swam spatial Optimization algorithm based on genetic mechanism and generalized Voronoi diagram in this paper, which can improve the performance of POS. The computational experiment for spatial optimization of fire stations in Nanjing shows that the proposed location model and optimization algorithm have achieved ideal result, the approaches can be applied to spatial optimization of maximal covering location for emergency facilities in urbanized area.