The content and structure of typical power emergency plans are analyzed. A formalization method for emergency plans based on ontology is proposed. The main concepts including organization， event， rule， action， constraint and resource are defined. The relationships between various concepts are concluded. A relational database model is employed to save the digitalized emergency plan. Three methods of information retrieval including full text retrieval， data retrieval and knowledge retrieval are suggested to apply to different kinds of users with their individual information requirements and characteristics. The emergency plan from an electric company is presented as a real-world case to prove the feasibility of the proposed method.