Reducing carbon emissions on the power generation side is the key to building a new power system and achieving the“carbon peak and carbon neutrality”goal in China. The essence of the impact of electricity spot market operation on carbon emissions in the power generation industry is achieved through its impact on the power generation structure. A theoretical priority curve for power generation is constructed based on the marginal cost of generating units. By comparing the power generation cost and carbon emissions between economic dispatch and real dispatch, the impact of spot market on power generation cost efficiency and carbon emissions is analyzed using multiple linear regression method. The research results indicate that during the trial operation of the Guangdong spot electricity market, the total cost of power generation significantly decreases, but the total carbon emissions of electricity will also change. Therefore, it is recommended to accelerate the entry of the spot market into formal operation on the one hand, and further integrate the electricity market with the carbon market on the other hand.