The hazardous materials on highway are becoming a lot of mobile hazardous sources. If the accidents occur, they can produce great influences for people, property and environment. With the development of economic, the transport volume of hazardous material is considerably increasing, and the potential risk of hazardous material for environment and mankind is enlarging. How to select the best transportation route, insure transportation safety and reach destination rapidly is an important problem for decision department. Aim at transportation network of hazardous materials, this paper studied the resultant impedance of each road. Then this paper turned the hazardous material highway transportation route decision-making problem into a single objective shortest path problem and applies the improved cellular automata model to solve it. Finally, an example confirmed the feasibility of the decision-making method. The decision-making method of hazardous material can help the government supervision and management department choose the best route.