Abstract: Existing researches on ontology in the power quality domain have such disadvantages as lack of standardized construction method, unclear relationships between terms and poor practicability, as well as the inability to automatically update with the domain development. Aiming at the above problems, an ontology construction method based on power quality standard files is proposed. Firstly, the sentence structure and semantic relationship in the power quality standard files are analyzed to form a relationship function to realize the semantic association between terms. Secondly, the text is processed and domain terms are extracted by building a professional vocabulary of power quality and adopting natural language processing technology. Then,according to the domain terms and their functional relationships, the specific terms are mapped to different instances in the ontology unit framework to construct an ontology unit in the power quality domain in four dimensions of stage, phenomenon, object and technical supervision. Finally, based on the technical requirements of power quality at different stages, an ontology model with close multi-dimensional knowledge connections is formed. The construction method can use standard files to build ontology models of different analysis objects at various stages, and support data sharing between systems and human-computer interaction in Chinese. The modeling process is simple and easy to standardize. And the ontology can be updated with the revision of standard files, so it has good practicality.