This paper analyzes the diffusion of evacuation advisory warnings during regional evacuations for accidents that release toxic vapors. Investigations results on the propagation of evacuation advisory warnings in the '4.16' chlorine release and the explosion accident at Chongqing Tianyuan Chemical Factory in China, and a comparison analysis of the evacuation notification process of six typical leakage accidents are presented in this paper. After conducting the evacuation notification investigation on the '4.16' accident, in which 401 valid questionnaires were collected from people who should have evacuated during the accident, the methods and channels of the evacuation notification, the notification efficiency, and the actual response efficiency of the recipients after the issuing of the evacuation advisory warnings were analyzed. A comparison analysis of the evacuation notification process is performed by analyzing six typical leakage accidents, and basic principles of evacuation notification for a regional evacuation for toxic vapor release accidents are proposed.