The accurate and reasonable calculation of the carbon emission factors on the electricity-consumption side is of great significance for the accurate assessment of the carbon emissions caused by electricity consumption of various regions, industries and enterprises. In this paper, a calculation model and method of carbon emission factors of corporate electricity consumption is constructed by combining power flow tracing and green power trading. Based on the power production and consumption data, power flow distribution data and green power trading data of power generation and consumption enterprises, the relationship among the carbon emissions on the electricity consumption side and the enterprise location, power consumption period and green power trading is researched to achieve real-time update of carbon emission factors on the electricity consumption side. Finally, the cases calculations on both IEEE 30-bus and an actual provincial power grid verify the effectiveness of the proposed method.