The invention discloses a method for processing a large SCL (substation configuration language) document. Due to performance of a document object model DOM, an SCL configuration tool achieved by the DOM is not applicable to processing the SCD (substation configuration description) documents. The method is characterized by comprising the following steps of: reading the SCL document completely to acomputer memory and analyzing the node information included in the document when reading-in the document and finding out the relative position where node elements are stored in the document and information of data in the nodes; in process of configuring a transformer substation, achieving the configuration by means of SCL cache control when addition, update and deletion of equipment are related to changing the content of the SCL document, wherein the cache control temporarily stores editing operations of the SCL document on the memory or a disc and the operations are written to an original SCL document when the user stores the SCL document. The invention has the advantages of less consumption of computer resources in the processing and also improves the processing efficiency of the large SCL document.