Abstract: The net ecosystem CO₂ exchange (NEE), gross primary productivity (GPP) and ecosystem respiration (R_eco) in the Liao river estuarine reed wetland of China were measured and analyzed by using eddy covariance technique from July to December of 2018. And then the variation patterns of NEE and related affecting factors were investigated. The results indicated that the diurnal variation curves of NEE in different months (from July to October) of the growing season showed a similar U shape, but the magnitudes of the diurnal variation of NEE were quite different. In November and December, the ecosystem showed weak net CO₂ releases, the diurnal variation trajectories of NEE were consistent with the temperature fluctuations. The GPP, R_eco and NEE values were all higher in growing season (from July to October) and lower in non-growing season (from November to December) in the reed wetland. From July to October, CO₂ exchange in daytime was mainly affected by the photosynthesis of reed, and there were rectangular hyperbolic relationships between daytime NEE and photosynthetically active radiation (PAR). PAR could explain 45%～54% of the variations of the daytime NEE. From July to December, the nighttime R_eco was exponentially correlated with air temperature. Air temperature could explain 62% of the variation of R_eco, and the temperature sensitivity of the ecosystem respiration (Q₁₀) was 2.20. In the second half of 2018, the Liao river estuarine reed wetland ecosystem was an obvious carbon sink (−81.38 g C/m²) with a cumulative emission of 278.29 g C/m² and a cumulative aborption of 359.67 g C/m².