Due to the large-scale development of rooftop photovoltaics and the continuous improvement of the national carbon trading market, the carbon credits generated by rooftop photovoltaics power generation can obtain additional income through carbon allocation offset or participation in carbon trading market. Firstly, the path and methods of participating in the carbon trading market for rooftop photovoltaic projects are studied, focusing on how large-scale rooftop photovoltaic projects participate in the carbon trading market and the degree of impact on the project's economy. Secondly, the life-cycle economic model of rooftop photovoltaic with carbon trading income is established based on the power generation model. Thirdly, in order to quantitatively analyze the income of carbon trading, an improved grey prediction GM(1, 1) model based on the differential threshold filtering method is proposed to predict the future carbon price. Finally, an example of large-scale rooftop photovoltaic is analyzed. The results show that large-scale rooftop photovoltaic considering participation in the carbon trading market has a relatively significant economic improvement.