The diagram of influence for the fire-extinguishing activity of a fire station is represented by various Voronoi diagrams of the fire station. The ordinary Voronoi diagram, the network Voronoi diagram, high order network Voronoi diagram and the weighted network Voronoi diagram are introduced and defined for use in fire-fighting strategy. The Voronoi diagrams of the fire stations have been calculated and drawn on the personal computer from the actual city-map data of the metropolitan district in Japan. The reasonable scopes of influence for the fire-fighting of the fire stations are represented by the ordinary Voronoi diagram and the locus problems of the fire stations in the provincial towns may be estimated by the calculational result of ordinary Voronoi diagram. However, the locus problem in the metropolitan area must be estimated by the network Voronoi diagram in due consideration of the traffic congestion. In the fire-fighting strategy, the calculational results of the high order weighted network Voronoi diagram of the fire station may be capable to the dynamic allocations of the fire engines from the fire station to fire scene and to other fire station at the traffic snarl and the lane loading in the metropolitan district.