The accurate, objective and effective method for accounting carbon emission is an urgent need to serve the goal of "carbon peak, carbon neutrality" and support scientific carbon emission reduction decisions. At present, indirect carbon emission has been included in several provincial carbon emission trading markets, and it is also an important emission source of carbon emission statistical accounting by all levels of administrative agencies. Therefore, the carbon emission factor of the power grid has a great impact on the overall situation of the national carbon emission reduction work, so it is of great significance to timely improve the carbon emission factor calculation method according to the needs of the new situation. Firstly, this paper discusses the concept and application scope of the carbon emission factor. Then the development of international carbon emission factors is summarized. Based on the current commonly used carbon emission factor calculation method in China, optimization suggestions are put forward from the aspects of accounting cycle and accounting scope, and the power grid carbon emission factor typical algorithm considering the impact of green power consumption is designed. The result of an example shows that the proposed algorithm can more accurately reflect the indirect carbon emission level reflecting users′ electricity consumption behavior, and promote the development of green power consumption more effectively.