Estuary holds a key position in linking the four geo-spheres, i.e., atmosphere, lithosphere, hydrosphere and biosphere. Figuring out the transfer mechanisms of estuarine carbon, especially the exchange of CO2 at the airwater interface is conducive to understanding the carbon pattern in coastal oceans. To date, many fruitful studies have been conducted on the control mechanism towards the partial pressure of CO2 (pCO2) in different estuarine areas around the world. By a thorough research on the latest studies of estuarine CO2 exchange with the atmosphere, it is concluded as follows: ①A common pattern is found on the spatial distribution of pCO2 in different estuarine areas. However, the concrete seasonal change of pCO2 shows great differences, and the corresponding control factors also vary considerably. ②Estuaries are believed to be large sources of CO2 to the atmosphere. It is estimated that the global estuarine CO2 degassing fluxes, although the global surface area of estuaries is small, are up to 0.25×1015~0.50×1015g C/a; and about 1/3 of riverine carbon is released into the atmosphere during the estuarine transit. ③Degradation of organic matter, lateral transfer of marshderived CO2 , mineral deposits in water and turbulence in the liquid phase are the main factors that are responsible for the emission of estuarine CO2 . At present, this estimate of estuarine CO2 exchange with the atmosphere is based on limited spatial data, therefore problems such as the limitation in the depth and scope of studies still exist. There are also varieties of uncertainties in the estimation of gas transfer velocity and the whole areas of global estuaries, all of them make it difficult to reach an accurate evaluation of CO2 fluxes at the airwater interface. It is difficult to predict the future trend of the CO2 exchange at the air-water interface due to the complexities of the driving forces and feedback mechanisms in estuarine carbon cycle and the intense anthropogenic disturbance. Investigating the mechanism of pCO2 in estuarine areas, improving the accuracy of evaluation of CO2 fluxes and comparing studies of different estuaries would be new scopes in the future researches on the exchange of CO2 at the air-water interface in estuaries.