Granular activated carbon that had been used in fuchsine dye-solution was regenerated by heating in a 1 m vertical quartz tube furnace at 400-800 ℃ using a mixture of carbon dioxide, steam and nitrogen as activating gases, whose composition was nearly equal to that of commercial oil-fired flue gas. By measuring the fuchsine-adsorption capacity, the iodine number and the physical properties of the active carbon regenerated, the optimal regenerating conditions were determined to give the reaction temperature of 650 ℃, the activating time of 20 min and the feed gas flow rate of 0.67 ㎥ STP/㎏-carbon. Under these conditions, carbon loss during the regenerating operation could be reduced below 2 % and thus the results here may be applied to the design of a large-scale unit. It is also suggested that oil combustion gas may be used as an activating agent for the regeneration of the granular active carbon.