In order to assess the effect of seaweed aquaculture on sea-air CO2 flux, a large-scale seaweed aquaculture area which is located in Lidao Bay, was selected as the investigation area. Based on the investigation data of pH, total alkalinity (TA), Chl-a, etc. during four cruises from April 2011 to January 2012, the spatial and seasonal variations of dissolved inorganic carbon (DIC) system parameters and aqueous pCO2 were investigated.Results showed that the mean annual concentrations of DIC, HCO-3, CO2-3 and CO2 were 2 024.8±147.0μmol/L, 1 842.4±132.1 μmol/L, 170.0±42.8μmol/L and 12.4±2.5 μmol/L, respectively. There were no significant differences between areas in concentrations of DIC and HCO-3(P> 0.05), while the differences for the concentration of CO2 were highly significant(P< 0.01).The mean annual values of aqueous pCO2 and sea-air CO2 flux were 287.8±37.9 μatm and -32.7±17.2 μmol/m2•d, respectively. There were highly significant differences(P< 0.01) for aqueous pCO2 and sea-air CO2 flux not only between different areas, but also between different seasons.Seaweed aquaculture is helpful for the diffusion of CO2 across the sea-air interface.