On the basis of field data measured during four cruises from April 2011 to January 2012, spatial and seasonal variations of CO2 dynamics and aqueous pCO2 were investigated in the seaweed aquaculture area, Lidao town, China. Results showed that the mean annual concentrations of dissolved inorganic carbon (DIC), HCO3−, CO32−, and CO2 were 2024.79 ± 146.96, 1842.41 ± 132.13, 170.02 ± 42.82, and 12.35 ± 2.52 µmol/L, respectively. There were no significant differences between areas in concentrations of DIC and HCO3− (P > 0.05), while the differences for the concentration of CO2 was very significant (P < 0.01). The mean annual values of aqueous pCO2 and sea-air CO2 flux were 287.80 ± 37.90 µatm and −32.71 ± 17.23 mmol/m2/d, respectively. There were very significant differences (P < 0.01) for aqueous pCO2 and sea-air CO2 flux not only between different areas, but also between different seasons. The buffer factor β indicates that, inside the seaweed area, inorganic carbon dynamics are mainly influenced by photosynthesis and respiration process.