This study looks to extract the public relations models (James Grunig) practiced in post disaster diplomacy by the Algerian government related to the 21 May 2003 BOUMERDES Earthquake and their roles in internal/external communication. This research is using the complex adaptive system approach to analyze and understand disaster diplomacy related activities done by foreign states in goal to know the communication process at the external level. As findings from this study; Public relations models at the external level are divided relatively to the purpose of practice into communication diplomacy and public relations. Communication diplomacy refers to the activities done within public information and two-way symmetric models. Communication diplomacy makes the disaster diplomacy legitimate, which creates equal power, good relations, long-term relations, good reputation and promotes disaster diplomacy between states. Public relations in the external communication refer to the activities done within press agentry and two-way asymmetric models. Public relations make the disaster diplomacy illegitimate, which creates non equal power, bad relations, short-term relations, bad reputation, and inhibit disaster diplomacy between states.