The partial pressure of carbon dioxide (pCO2) in the surface seawater of the South Yellow Sea(SYS) was investigated by means of cruising observation during the spring of 2007. The distribution characters and influencing factors of the pCO2 were studied by combining with the cogredient data of the seawater temperature, salinity, chlorophyll, pH. The results showed that the values of the pCO2 in the surface seawater of the SYS was in the range of 365.2~734.9 μatm, with an average of 548.0 μatm, the maximum value appeared in sea area near 121.5°E, 33.4°N, and the minimum value appeared in sea area near 123°E, 32.3°N. As a whole the distribution of the pCO2 present obvious horizontal inhomogeneity, gradually decreased from west to east, and was higher at the middle latitude than both sides under the combined influence of biological, hydrological and chemical factors. The pCO2 was in direct proportion to the seawater temperature and in inverse proportion to the seawater salinity in the shoal-water area along the northern coast of Jiangsu Province and the near shore area of southern Shandong Province, but there was a reverse trend at the mouth of Yangtze River. In addition, there was a negative correlation between the pCO2 and the chlorophyll as well as between the pCO2 and the pH value in the whole investigated sea area. In this study, it was the first time that one of two CO2 analyzers was calibrated by series-connecting one of the channels, meanwhile, the other analyzer was calibrated with the standard gas of carbon dioxide through the other channel. Therefore, the concentrations of carbon dioxide in air and seawater could be continuously monitored. It was proved that the method was simple to operate, and the data obtained were accurate and reliable, with the hope of providing technical support for capacity building on energy conservation and emission reduction.