Against the backdrop of global warming, extreme high-temperature events are becoming more frequent and intense. Lake heatwaves, as a typical manifestation, can alter the production and emission processes of CO2 in shallow lakes over short time scales, thereby affecting the accuracy of CO2 budget estimates in lake ecosystems. To investigate the effects of short-term heatwaves on CO2 production and emissions in shallow lakes and to explore the response characteristics and related influencing factors, this study conducted experiments using the "Smart Lake" mesocosm simulation system at the Taihu Lake Dongshan Station. A heatwave group (+8°C) and a control group (ambient temperature) were established. Based on observations and estimations during three periods (pre-heatwave, during heatwave, and post-heatwave), we analyzed the variations in pCO2 in surface water and sediment pore water, as well as diffusive CO2 fluxes at the water-air interface and the sediment-water interface. The relationships between surface water pCO2 and major environmental variables were also explored. The results showed that during the heatwave, pCO2 increased in both groups, but the increase was greater in the heatwave group, reaching a mean value of 860 ± 54 μatm, compared to 606 ± 37 μatm in the control group. Meanwhile, the water-air pCO2 flux in the heatwave group was significantly enhanced during the heatwave, at 31.2 ± 3.1 mmol m?² d?¹, higher than that of the control group (19.2 ± 5.0 mmol m?² d?¹). In contrast, the sediment-water interface flux in the heatwave group was relatively small, only 1.3 ± 0.2 mmol m?² d?¹, indicating that CO2 production and emissions from sediments alone cannot explain the enhancement of the water-air CO2 emission flux during the heatwave. Partial correlation analysis showed that after controlling for the effect of water temperature, the correlations between surface water pCO2 and environmental variables in the heatwave group were not significant, suggesting the effects of environment variables in CO? were mainly driven by changes in water temperature. Overall, short-term winter heatwave events can significantly alter CO2 dynamics variability in the water-sediment system of shallow lakes, but the biological metabolic processes and physicochemical mechanisms underlying these responses still require further investigate.