A systematic investigation along with field measurements were performed at the Mt. Changbai volcanic field on the border between China and North Korea from June to September in 2016, with respect to geological sources of degassed CO₂ and its relationship with fluids between the monogenetic and polygenetic volcanoes. Our estimates indicate that the flux of CO₂ degassing from the polygenetic and monogenetic volcanoes in the Mt. Changbai volcanic field is 1.8 × 10⁵ t/yr, which corresponds to the middle level of CO₂ output from volcanic fields in the world. The flux of CO₂ degassing from the soil shows a decreasing trend with distance from the Tianchi polygenetic volcanic caldera. Temporal variations of contrast value in the Tianchi polygenetic volcanic caldera and peripheral areas are more conformable than those in the monogenetic volcanoes. Based on the analysis to the soil CO₂ fluxes, we propose that monitoring CO₂ fluxes in the polygenetic volcanic caldera and peripheral areas would provide useful information about the local volcanic activity, especially in dormant volcanoes like the Tianchi polygenetic volcanic caldera. Other CO₂ flux measurement sites not only related to the Tianchi caldera area should also be selected for future volcanic monitoring.