Abstract: This study takes some thermal power plants that have completed ultra-low emission retrofits in Yunnan Province as the research object. Through coordinate control effect coordinate system analysis method and pollutant emission reduction cross-elastic analysis method, the synergistic emission reduction effects between PM₁₀, SO₂, NOx and carbon dioxide were analyzed. The results showed that two of three thermal power plants do not have a synergistic emission reduction effect between carbon dioxide and atmospheric pollutants, but the other one does. The results may be caused by the large difference in the load rate before and after the ultra-low emission retrofit. Whether the ultra-low emission retrofit of thermal power plants has a synergistic emission reduction effect on atmospheric pollutants and carbon dioxide need further study.