Conventional Voronoi diagram can only be used in route planning with the same threats, which is limited in application for actual battlefield environment.We proposed an improved Voronoi diagram based on Delaunay triangulation, and applied it to route planning with different threats.The construction of the improved Voronoi, the obtaining of starting path and ending path were mainly discussed in the paper.Finally the route planning based on the improved Voronoi was completed on the platform of VC++6.0.The result shows that the planned route can effectively avoid the threats as radars, which proves the feasibility of the improved Voronoi in route planning with different threats.