his study introduces an approach to isolate the packing area from the whole rotating packed bed (RPB) by N2 flow and measures the effective mass transfer area in the shell zone. On the basis of the chemical absorption of CO2 in NaOH aqueous solution, experiments are carried out to detect the effects of rotating speed, temperature, liquid flow rate, and gas flow rate on the effective mass transfer area. Experimental results show that the effective mass transfer area in the RPB is independent of temperature and gas flow rate and in direct proportion to the liquid flow rate and rotating speed. In the same experimental conditions, the shell zone effective mass transfer area takes up around 30% of the whole RPB effective mass transfer area, while the packing area takes up the other 70%. In our settings, the effective use ratio of packing area can be a minimum of 25% and a maximum of 90%.