This study reports thus far a most comprehensive dataset of surface seawater pCO2 (partial pressure of CO2) and the associated air-sea CO2 fluxes in the largest marginal sea in North Pacific, the South China Sea (SCS) based on 47 surveys conducted in 2000-2018. We categorized the SCS into five different domains featured with different physics and biogeochemistry to better characterize the seasonality of the pCO2 dynamics and to better constrain the CO2 flux. The five domains are (A) the northern SCS shelf, (B) the northern SCS slope, (C) the SCS basin, (D) West of Luzon Strait, and (E) western SCS. We showed highly dynamic spatial variability of sea surface pCO2 in the SCS except in winter when it ranged in a narrow band of 330 to 370 matm, while pCO2 in other seasons showed large variability. In general, surface water pCO2 in the northern SCS (Domains A, B and D) showed seasonal variation with low values in cold season and high values in warm season, except in the Pearl River plume (200-500 matm) and the area off northwest Luzon where winter upwelling occurred (370-390 matm). In the SCS basin and the western SCS (Domains C and E), surface water pCO2 was generally higher than that of the atmosphere (380-420 matm). Additionally, large intra-seasonal variation occurred. In spring, pCO2 increased with temperature in the northern SCS. It was a CO2 sink in March and CO2 source in May, while it was transitional system from sink to source in April. The area-weighted CO2 flux in the entire SCS was -1.1±2.2 mmol m^-2 d^-1 in winter, 0.9±0.9 mmol m^-2 d^-1 in spring, 2.5±1.4 mmol m^-2 d^-1 in summer and 1.9±1.1 mmol m^-2 d^-1 in fall. It is important to note that the standard deviations in these flux ranges mostly reflect the spatial variation of pCO2 rather than the bulk uncertainty. Nevertheless, on an annual basis, the average CO2 influx into the entire SCS shelf was 1.2±1.7 mmol m^-2 d^-1.