In a stirred vessel with the aspect ratio of 2.4, the gas-liquid mass transfer characteristics of triple-impeller configurations with surface aeration have been studied. The way by adding one or more impellers below the aerating impeller could not overcome the problem of poor gas dispersion in the region close to the bottom of the gas-liquid vessel stirred only by a surface aerator. With the combination of surface aeration and sparger aeration, gas dispersion is greatly improved. Triple-inipeller configurations and volumetric gas flow rates are optimized based on the volumetric mass transfer coefficient per power consumption. It is found that the sparging gas has only a little effect on the surface aeration, because the vessel is stirred by the triple-impeller configuration and with a larger aspect ratio.