Abstract: Scenario construction and deduction of unconventional emergencies is one of the key issues in the “Scenario-Response” type emergency management model. After analyzing the characteristics of emergency management and the extant related studies, we build a methodology of scenario construction and deduction for emergencies, which includes four parts: the extraction and representation methods of the key emergency elements and the mechanisms among the elements; scenario construction methods under multi-source information fusion, scenario deduction methods based on “Scenario-Response”, and the assessment methods of scenario deduction results and actual effects. The proposed system is beneficial to solve the key issues of “Scenario-Response” emergency management, which can promote the implementation of “Scenario-Response” methodology in emergency management practice and improve the decision support for governments’ responses to unconventional emergencies.