The invention discloses a mirror image method for metadata. The content of the metadata is saved by adopting a serialization file, when the data are written, the data are serialized to be a specified file, then the file is reversely serialized to update a metadata object, the metadata update all the mirror images through copy, and synchronization of the data is ensured during concurrent writing. When the metadata are read, the metadata object determines which image object for access. Besides, when the metadata are provided, in order to reflect constant change of power data, two types of incident triggering methods changing according to a fixed time frequency and data are added to the metadata, so that convenience is provided for a user of the metadata. Due to the fact that the mirror image technology of the metadata is adopted, load balance of concurrent access and access of the data is achieved, access response speed is improved, and meanwhile access reliability and stability are also improved.