The invention relates to an electricity sales distribution method and system, wherein the method comprises the steps of: according to the power transmission and distribution real cost-benefit data of a power grid, obtaining the power transmission and distribution allowance benefit parameter of the power grid; according to the ratio between the power transmission and distribution allowance benefit parameter and a preset original value of fixed assets, obtaining the allowance benefit index of each voltage grade; according to the electric power quantity balance data and electric power loss data of each voltage grade, separately obtaining the total power transmission and distribution amount of each voltage grade; processing the allowance benefit index and the total power transmission and distribution amount of each voltage grade to obtain the transmission and distribution electrovalence calculation value of each voltage grade; and according to the transmission and distribution electrovalence calculation value, establishing an electricity sales forecasting function, and according to the electricity sales forecasting function, obtaining the electricity sales distribution value of each voltage grade. Based on power grid electric power operation parameters, the electricity sales distribution method and system can obtain the transmission and distribution electrovalence calculation value to accurately reflect power grid enterprise costs so as to provide accurate data support for reasonable electricity sales distribution.