Against the backdrop of increasing concerns about global climate change and environmental protection, the building sector, as an important source of carbon emissions, has gradually become a focus of research. In particular, residential buildings in severe cold regions have more significant carbon emissions due to the long-time heating demand. This paper studies the carbon emissions of ultra-low-energy residential buildings in cold regions, and analyzes different energy consumption and its carbon emissions by establishing a carbon emission measurement model. Firstly, the carbon emission coefficient method is used to measure the carbon emissions of residential buildings in the operation stage. The results of the analysis show that the carbon emissions of buildings in severe cold regions are significantly affected by the type of energy consumption and seasonal changes. In the empirical analysis, the winter carbon emissions of the 150-unit type reached 1408.6 kg in December and January, showing the characteristics of high carbon emissions in winter. In addition, by simulating the carbon emission and thermal comfort of different cities, Wuhan has the highest total carbon emission of 93127.83 kg, while Chengdu and Shanghai are 76216.06 kg and 81730.77 kg, respectively, showing the influence of different geographical climates on carbon emission. The study further used sensitivity analysis to assess the impact of different factors on carbon emissions, and the results showed that factors such as population size, urbanization rate and per capita GDP had a significant positive impact on carbon emissions. The study suggests that in the future, when designing ultra-lowenergy buildings, the focus needs to be on optimizing the efficiency of energy use, especially energy management during the winter heating phase, in order to reduce carbon emissions and enhance the sustainability of energy use.