Carbon dioxide(CO_2) emission from the rivertype reservoir is an hotspot of carbon cycle within inland waters. However, related studies on the different types of reservoirs are still inadequate. Therefore, we sampled the Three Gorges Reservoir(TGR), a typical river-type reservoir having both river and lake characteristics, using an online system(HydroCTM/CO_2) and YSI-6600v2 meter to determine the partial pressure of carbon dioxide(pCO_2)and physical chemical parameters in 2013. The results showed that the CO_2 flux from the mainstream ranged from 26.1 to 92.2 mg CO_2/m~2h with average CO_2 fluxes of 50.0 mg/m~2h. The CO_2 fluxes from the tributary ranged from-10.91 to 53.95 mg CO_22/mh with area-weighted average CO_2 fluxes of 11.4 mg/m~2h. The main stream emits CO_2 to the atmosphere the whole year; however, the surface water of the tributary can sometimes act as a sink of CO_2 for the atmosphere. As the operation of the TGR, the tributary became more favorable to photosynthetic uptake of CO_2 especially in summer. The total CO_2 flux was estimated to be 0.34 and 0.03 Tg CO_2/year from the mainstream and the tributaries, respectively. Our emission rates are lower than previous estimates, but they are in agreement with the average CO_2 flux from temperate reservoirs estimated by Barros et al.(Nat Geosci 4(9):593–596, 2011). Carbon dioxide (CO 2) emission from the rivertype reservoir is an hotspot of carbon cycle within inland waters. However, we sampled the Three Gorges Reservoir (TGR), a typical river- type reservoir having both river and lake characteristics, using an online system (HydroCTM / CO_2) and YSI-6600v2 meter to determine the partial pressure of carbon dioxide (pCO_2) and physical chemical parameters in 2013. The results showed the CO_2 flux from the The main ranged from 26.1 to 92.2 mg CO 2 / m ~ 2h with average CO 2 fluxes of 50.0 mg / m ~ 2h. The CO_2 fluxes from the tributary ranged from-10.91 to 53.95 mg CO_22 / mh with area-weighted average CO_2 fluxes of 11.4 mg / m ~ 2h. The main stream emits CO_2 to the atmosphere the whole year; however, the surface water of the tributary can sometimes act as a sink of CO_2 for the atmosphere. As the operation of the TGR, the tributary became more favorable to photosynthetic upta The total CO_2 flux was estimated to be 0.34 and 0.03 Tg CO_2 / year from the mainstream and the tributaries, respectively. Our emission rates are lower than previous estimates, but they are in agreement with the average CO_2 flux from temperate reservoirs estimated by Barros et al. (Nat Geosci 4 (9): 593-596, 2011).