Abstract: The study of scenario, which is a base of emergency plan and emergency preparing, is located in a basic research in emergency management. By case analysis and logic reasoning, the composition of scenario elements which include three dimensions of disaster system, counter-disaster system, and victims is confirmed. A visualization method of scenario expression is suggested. The expression of scenario needs to determine the key elements of a scenario and analyze the relationships among the elements of a scenario. The disassemble of scenarios in space and the evolution of scenario with time are studied, and the relationship of scenarios is discussed