Abstract:The importance of the rationalization of electricity transmission and distribution is explained. Firstly，the classification and calculation of fixed costs，and details of the existing fixed cost allocation methods are described. The focus of the article is the detailed classification of fixed costs according to the characterization of the large consumers direct purchase of electricity between provinces. For costs of different types，due to the different factors which can affect it，different distribution methods are applied to make the fixed cost shared by the various transactions more reasonable，accurate.