To explore the diurnal variation characteristics and influencing factors of greenhouse gases in grass carp polyculture and monoculture ponds,24-hour monitoring was carried out to measure the CO2 ,(Methane) CH4 ,and (Nitrous oxide)N2 O fluxes at the water-air interface of two grass carp culture ponds using static chamber-GC method.The study indicated that the diurnal variation range of CO2 fluxes were (-119.03± 76.25)-(59.79±52.19) mg/(m2·h) in the polyculture and (-199.88±163.25)-(186.64±48.06) mg/(m2·h) in the monoculture.The range of CH4 fluxes were (1.81±2.07)-(7.25±7.06) and (-11.75± 14.38)-(17.77±14.84)mg/(m2·h).The range of N2 O fluxes were(24.4±16.4)-(77.4±34.7) and (43.8±12.8)-(165.7±122.2)μg/(m2·h).The average daily emission fluxes in the polyculture of CO2 , CH4 and N2 O were lower than those in the monoculture.Among them,N2 O emission reached an extremely significant level.The polyculture led to reductions in the average emission fluxes of CO2 ,CH4 and N2 O from grass carp ponds by 56.60%,5.03%,and 46.96%.The two farming modes were both greenhouse gas emission sources.The emissions of the three greenhouse gases were lower during the day and higher at night.The diurnal difference in CO2 flux between the two modes reached an extremely significant level.The diurnal difference in CH4 emission from monoculture reached a significant level.There was no significant difference between the two modes of N2 O emission.The major environmental influencing factors of greenhouse gas emissions in polyculture were (Oxidation-reduction Potential)Eh,(Chemical Oxygen Demand)COD,(Total Organic Carbon)TOC,and air pressure,while those in the monoculture were wind speed,air pressure,and mud temperature.The polyculture can reduce greenhouse gas emissions from grass carp ponds,which has a significant carbon emission reduction effect.