To investigate the characteristics of CO₂， CH₄， and N₂O fluxes and their driving factors in typical grass carp （Ctenopharyngodon idella） ponds， in-situ monitoring of gas fluxes was conducted using the static chamber-gas chromatography method in ponds containing 1-year-old （GC1）， 2-year-old （GC2）， and 3-year-old （GC3） grass carp. The emission intensity and its relationship with environmental factors were analyzed. Results showed that the order of greenhouse gas fluxes was GC3 > GC2 > GC1. The mean fluxes of CO₂， CH₄， and N₂O in GC3 ponds were 42.30 mg/（m²·h）， 13.31 mg/（m²·h）， and 567.25 μg/（m²·h）， respectively. All ponds acted as sources of CH₄. Redundancy analysis indicated that gas fluxes in GC1 were primarily influenced by NO₃^--N and sediment temperature， water temperature was the dominant factor in GC2， and sediment temperature and dissolved oxygen controlled the fluxes in GC3. Analysis of direct emission factors revealed that the CO₂， CH₄， and N₂O emission factors in GC3 ponds were 132.98， 41.91， and 1.77 g/kg， respectively， all significantly higher than those in GC1 and GC2 （P<0.05）. The global warming potential per unit area followed the order GC3 （53.48 t CO₂-eq/hm²）>GC2 （31.84 t CO₂-eq/hm²）>GC1 （6.54 t CO₂-eq/hm²）， with significant differences （P<0.05）. The GHG emission intensity per unit fish yield was 0.26， 1.05， and 1.95 t CO₂-eq/t for GC1， GC2， and GC3， respectively， showing significant differences （P<0.05）. This study demonstrates that culturing size significantly affects the GHG emission intensity in grass carp ponds， with elevated temperatures and larger fish size exacerbating carbon emissions. It is suggested that regulating the aquaculture structure and key environmental factors can promote the achievement of carbon neutrality in fisheries.