Objective：To strengthen the research on theory and method of early warning for emergent public health event, so as to obtain timely information, correctly analyze the situation, and apply effective measures when the event happens. Methods: The definition of vulnerability of emergent public health event and the vulnerability factors were discussed. The indicator system and the evaluating method for public health vulnerability were systematically studied. The extenics theory and the theory of vulnerability evaluation were used for warning exercise. Results: We constructed an extenics model for early warning of emergent public health event; the model was used to evaluate the public health of a population. Conclusion: The theory of vulnerability evaluation is introduced in emergent public health event to construct an extenics model for early warning of emergent public health event; the model can be used to evaluate the public health of certain population.