Before culturing adult Chinese mitten crabs (Eriocheir sinensis), aquaculture ponds are sun-dried to enhance the bottom environment for the next cultivation stage. However, during the sunning stage, the sediment in these ponds may release significant amounts of CO₂ into the atmosphere. We focused on E. sinensis aquaculture ponds in Suqian, Jiangsu Province, using soil carbon flux measurement instruments to monitor and analyze CO₂ emission fluxes over two and a half months, from mid-December 2023 to early March 2024. Continuous monitoring was conducted both day and night to determine CO₂ emission fluxes throughout the sunning stage. CO₂ emission fluxes were measured three times a day and night on December 19, 2023, January 24, 2024, and February 28, 2024. Each monitoring session began at 8:00 AM and continued every three hours. Additional measurements were taken on December 14, 2023, December 24, 2023, January 4, 2024, January 14, 2024, January 24, 2024, February 3, 2024, February 13, 2024, February 23, 2024, and March 4, 2024, between 8:00–10:00 AM. Simultaneous meteorological and soil indicators were measured to analyze environmental factors affecting CO₂ emission fluxes. Results showed that the average daily CO₂ emission fluxes from the pond bottom after one week, one month, and two months of sunning were (1214±633) mg/(m²·d), (1055±422) mg/(m²·d), and (407±93) mg/(m²·d), respectively. Emission fluxes peaked in the afternoon and were lowest in the early morning. A diurnal pattern was observed, with higher emission fluxes during the day and lower at night. As sunning time extended, the day-night difference in emission fluxes gradually decreased, though a significant difference persisted. The range of CO₂ emission fluxes at the sediment-atmosphere interface during the sunning stage was 351– 2331 mg/(m²·d), with an average of (1040±647) mg/(m²·d). The CO₂ emission fluxes showed a trend of initial increase followed by a decrease, indicating that the entire sunning stage was a source of CO₂ emissions. Stepwise regression analysis identified soil temperature and soil porosity as the primary environmental factors influencing CO₂ emission fluxes. A significant positive correlation was found between soil temperature and CO₂ emission fluxes, while soil porosity was negatively correlated due to the effects of soil moisture and thermal conditions. Cumulative CO₂ emissions increased gradually, although the growth rate slowed over time, with total cumulative CO₂ emission fluxes during the sunning stage calculated at 89.3 g/m². In this study, we reveal the changes in CO₂ emission fluxes during the sunning stage of E. sinensis aquaculture ponds, highlighting these ponds as significant CO₂ emission sources during this period. There is substantial potential for CO₂ reduction in the E. sinensis aquaculture industry. The data provided by this study support efforts to reduce greenhouse gas emissions and develop corresponding emission reduction strategies in E. sinensis aquaculture ponds.