The possibility of influenza outbreak by Highly Pathogenic Avian Influenza(HPAI) is predicted, and concerns about the catastrophic results in society general are also raising. Many public health agencies, both national governmental agencies and international agencies such as World Health Organization(WHO) are making efforts to prepare for it. WHO issued guidelines and national checkpoint for its member states, sets up international preparedness plans in the year 1999 and 2005 in the name of "WHO Pandemic Influenza Response Plan", Pandemic Influenza can be categorized as a ’public health emergency of international concern’ in the IHR(2005)，which requires rigorous responses from national government as well as from international society. These responses are implemented by medical professionals, public health agency, national emergecy response institutions and citizens. Public health measures to prevent and constrain the spread of infectious agent mainly compose of governmental actions which, by its nature, can be coercive (against one’s free choices), and there is growing concern about this is another threat to humanity. Legal and ethical consideration is necessary to ensure the justifiable use of governmental powers and people’s compliance to public health measures. Law is necessary not only for ethical reasons alone, because any governmental activities can be implemented effectively if governmental agencies properly equipped with law. To evaluate legal and ethical aspects of pandemic influenza plan that government established, ethical principles that can guide moral justification were identified. Ethical principles addressed by American Public Health Association were critically reviewed for the purpose of establishing public health ethical principles in times of pandemic influenza. And principles public health practitioners should keep in mind all through the phases of pandemic influenza were identified. Current public health laws in Korea, were reviewed