With the rapid growing of massive digital resource, how to manage different formats of digital resources efficiently and search the needed recourses accurately is very difficult for knowledge management in electric power enterprises. Most of the traditional search methods are based on keyword matching and fail to consider the semantic information, so these methods cannot provide accurate, personalized learning resources for users and lead to a serious waste of resources and manpower. In order to solve this problem, this paper uses semantic metadata to descript various heterogeneous resources, and develop an power knowledge ontology annotation method. With the proposed method, the different formats of digital resources of the electric power company can be retrieved effectively and the knowledge sharing and reuse can be achieved.